diff --git a/webapp/src/Command/AbstractCompareCommand.php b/webapp/src/Command/AbstractCompareCommand.php
new file mode 100644
index 0000000000..99c0d2cfc4
--- /dev/null
+++ b/webapp/src/Command/AbstractCompareCommand.php
@@ -0,0 +1,96 @@
+<?php declare(strict_types=1);
+
+namespace App\Command;
+
+use App\Service\Compare\AbstractCompareService;
+use App\Service\Compare\Message;
+use App\Service\Compare\MessageType;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Style\SymfonyStyle;
+use Symfony\Component\Serializer\SerializerInterface;
+
+/**
+ * @template T
+ */
+abstract class AbstractCompareCommand extends Command
+{
+    /**
+     * @param AbstractCompareService<T> $compareService
+     */
+    public function __construct(
+        protected readonly SerializerInterface $serializer,
+        protected AbstractCompareService $compareService
+    ) {
+        parent::__construct();
+    }
+
+    protected function configure(): void
+    {
+        $this
+            ->addArgument('file1', InputArgument::REQUIRED, 'First file to compare')
+            ->addArgument('file2', InputArgument::REQUIRED, 'Second file to compare');
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output): int
+    {
+        $style = new SymfonyStyle($input, $output);
+        $messages = $this->compareService->compareFiles($input->getArgument('file1'), $input->getArgument('file2'));
+
+        return $this->displayMessages($style, $messages) ?? Command::SUCCESS;
+    }
+
+    /**
+     * @param Message[] $messages
+     */
+    protected function displayMessages(SymfonyStyle $style, array $messages): ?int
+    {
+        if (empty($messages)) {
+            $style->success('Files match fully');
+            return null;
+        }
+
+        $headers = ['Level', 'Message', 'Source', 'Target'];
+        $rows = [];
+        $counts = [];
+        foreach ($messages as $message) {
+            if (!isset($counts[$message->type->value])) {
+                $counts[$message->type->value] = 0;
+            }
+            $counts[$message->type->value]++;
+            $rows[] = [
+                $this->formatMessage($message->type, $message->type->value),
+                $this->formatMessage($message->type, $message->message),
+                $this->formatMessage($message->type, $message->source ?? ''),
+                $this->formatMessage($message->type, $message->target ?? ''),
+            ];
+        }
+        $style->table($headers, $rows);
+
+        $style->newLine();
+        foreach ($counts as $type => $count) {
+            $style->writeln($this->formatMessage(MessageType::from($type), sprintf('Found %d %s(s)', $count, $type)));
+        }
+
+        if (isset($counts['error'])) {
+            $style->error('Files have potential critical differences');
+            return Command::FAILURE;
+        }
+
+        $style->success('Files have differences but probably non critical');
+
+        return null;
+    }
+
+    protected function formatMessage(MessageType $level, string $message): string
+    {
+        $colors = [
+            MessageType::ERROR->value => 'red',
+            MessageType::WARNING->value => 'yellow',
+            MessageType::INFO->value => 'green',
+        ];
+        return sprintf('<fg=%s>%s</>', $colors[$level->value], $message);
+    }
+}
diff --git a/webapp/src/Command/CompareAwardsCommand.php b/webapp/src/Command/CompareAwardsCommand.php
new file mode 100644
index 0000000000..757c73f29c
--- /dev/null
+++ b/webapp/src/Command/CompareAwardsCommand.php
@@ -0,0 +1,25 @@
+<?php declare(strict_types=1);
+
+namespace App\Command;
+
+use App\DataTransferObject\Award;
+use App\Service\Compare\AwardCompareService;
+use Symfony\Component\Console\Attribute\AsCommand;
+use Symfony\Component\Serializer\SerializerInterface;
+
+/**
+ * @extends AbstractCompareCommand<Award[]>
+ */
+#[AsCommand(
+    name: 'compare:awards',
+    description: 'Compare awards between two files'
+)]
+class CompareAwardsCommand extends AbstractCompareCommand
+{
+    public function __construct(
+        SerializerInterface $serializer,
+        AwardCompareService $compareService
+    ) {
+        parent::__construct($serializer, $compareService);
+    }
+}
diff --git a/webapp/src/Command/CompareResultsCommand.php b/webapp/src/Command/CompareResultsCommand.php
new file mode 100644
index 0000000000..f12d0ced8e
--- /dev/null
+++ b/webapp/src/Command/CompareResultsCommand.php
@@ -0,0 +1,25 @@
+<?php declare(strict_types=1);
+
+namespace App\Command;
+
+use App\DataTransferObject\ResultRow;
+use App\Service\Compare\ResultsCompareService;
+use Symfony\Component\Console\Attribute\AsCommand;
+use Symfony\Component\Serializer\SerializerInterface;
+
+/**
+ * @extends AbstractCompareCommand<ResultRow[]>
+ */
+#[AsCommand(
+    name: 'compare:results',
+    description: 'Compare results between two files'
+)]
+class CompareResultsCommand extends AbstractCompareCommand
+{
+    public function __construct(
+        SerializerInterface $serializer,
+        ResultsCompareService $compareService
+    ) {
+        parent::__construct($serializer, $compareService);
+    }
+}
diff --git a/webapp/src/Command/CompareScoreboardCommand.php b/webapp/src/Command/CompareScoreboardCommand.php
new file mode 100644
index 0000000000..c4eb4b8c03
--- /dev/null
+++ b/webapp/src/Command/CompareScoreboardCommand.php
@@ -0,0 +1,25 @@
+<?php declare(strict_types=1);
+
+namespace App\Command;
+
+use App\DataTransferObject\Scoreboard\Scoreboard;
+use App\Service\Compare\ScoreboardCompareService;
+use Symfony\Component\Console\Attribute\AsCommand;
+use Symfony\Component\Serializer\SerializerInterface;
+
+/**
+ * @extends AbstractCompareCommand<Scoreboard>
+ */
+#[AsCommand(
+    name: 'compare:scoreboard',
+    description: 'Compare scoreboard between two files'
+)]
+class CompareScoreboardCommand extends AbstractCompareCommand
+{
+    public function __construct(
+        SerializerInterface $serializer,
+        ScoreboardCompareService $compareService
+    ) {
+        parent::__construct($serializer, $compareService);
+    }
+}
diff --git a/webapp/src/DataTransferObject/Award.php b/webapp/src/DataTransferObject/Award.php
index eb5f2ade8d..fa3fc8faeb 100644
--- a/webapp/src/DataTransferObject/Award.php
+++ b/webapp/src/DataTransferObject/Award.php
@@ -11,7 +11,7 @@ class Award
      */
     public function __construct(
         public readonly string $id,
-        public readonly string $citation,
+        public readonly ?string $citation,
         #[Serializer\Type('array<string>')]
         public readonly array $teamIds,
     ) {}
diff --git a/webapp/src/DataTransferObject/ContestState.php b/webapp/src/DataTransferObject/ContestState.php
index e10d0ef6ed..9296df9b5e 100644
--- a/webapp/src/DataTransferObject/ContestState.php
+++ b/webapp/src/DataTransferObject/ContestState.php
@@ -5,11 +5,11 @@
 class ContestState
 {
     public function __construct(
-        public readonly ?string $started,
-        public readonly ?string $ended,
-        public readonly ?string $frozen,
-        public readonly ?string $thawed,
-        public readonly ?string $finalized,
-        public readonly ?string $endOfUpdates,
+        public readonly ?string $started = null,
+        public readonly ?string $ended = null,
+        public readonly ?string $frozen = null,
+        public readonly ?string $thawed = null,
+        public readonly ?string $finalized = null,
+        public readonly ?string $endOfUpdates = null,
     ) {}
 }
diff --git a/webapp/src/DataTransferObject/Scoreboard/Problem.php b/webapp/src/DataTransferObject/Scoreboard/Problem.php
index 4f0d363825..b83613aa06 100644
--- a/webapp/src/DataTransferObject/Scoreboard/Problem.php
+++ b/webapp/src/DataTransferObject/Scoreboard/Problem.php
@@ -9,7 +9,7 @@ class Problem
 {
     public function __construct(
         #[Serializer\Groups([ARC::GROUP_NONSTRICT])]
-        public readonly string $label,
+        public readonly ?string $label,
         public readonly string $problemId,
         public readonly int $numJudged,
         public readonly int $numPending,
diff --git a/webapp/src/Service/Compare/AbstractCompareService.php b/webapp/src/Service/Compare/AbstractCompareService.php
new file mode 100644
index 0000000000..783bacba21
--- /dev/null
+++ b/webapp/src/Service/Compare/AbstractCompareService.php
@@ -0,0 +1,84 @@
+<?php declare(strict_types=1);
+
+namespace App\Service\Compare;
+
+use Symfony\Component\Serializer\Exception\ExceptionInterface;
+use Symfony\Component\Serializer\SerializerInterface;
+
+/**
+ * @template T
+ */
+abstract class AbstractCompareService
+{
+    /** @var Message[] */
+    protected array $messages = [];
+
+    public function __construct(protected readonly SerializerInterface $serializer) {}
+
+    /**
+     * @return Message[]
+     */
+    public function compareFiles(string $file1, string $file2): array
+    {
+        $success = true;
+        if (!file_exists($file1)) {
+            $this->addMessage(MessageType::ERROR, sprintf('File "%s" does not exist', $file1));
+            $success = false;
+        }
+        if (!file_exists($file2)) {
+            $this->addMessage(MessageType::ERROR, sprintf('File "%s" does not exist', $file2));
+            $success = false;
+        }
+        if (!$success) {
+            return $this->messages;
+        }
+
+        try {
+            $object1 = $this->parseFile($file1);
+        } catch (ExceptionInterface $e) {
+            $this->addMessage(MessageType::ERROR, sprintf('Error deserializing file "%s": %s', $file1, $e->getMessage()));
+        }
+        try {
+            $object2 = $this->parseFile($file2);
+        } catch (ExceptionInterface $e) {
+            $this->addMessage(MessageType::ERROR, sprintf('Error deserializing file "%s": %s', $file2, $e->getMessage()));
+        }
+
+        if (!isset($object1) || !isset($object2)) {
+            return $this->messages;
+        }
+
+        $this->compare($object1, $object2);
+
+        return $this->messages;
+    }
+
+    /**
+     * @return T|null
+     * @throws ExceptionInterface
+     */
+    abstract protected function parseFile(string $file);
+
+    /**
+     * @param T $object1
+     * @param T $object2
+     */
+    abstract public function compare($object1, $object2): void;
+
+    protected function addMessage(
+        MessageType $type,
+        string $message,
+        ?string $source = null,
+        ?string $target = null,
+    ): void {
+        $this->messages[] = new Message($type, $message, $source, $target);
+    }
+
+    /**
+     * @return Message[]
+     */
+    public function getMessages(): array
+    {
+        return $this->messages;
+    }
+}
diff --git a/webapp/src/Service/Compare/AwardCompareService.php b/webapp/src/Service/Compare/AwardCompareService.php
new file mode 100644
index 0000000000..961de608c7
--- /dev/null
+++ b/webapp/src/Service/Compare/AwardCompareService.php
@@ -0,0 +1,61 @@
+<?php declare(strict_types=1);
+
+namespace App\Service\Compare;
+
+use App\DataTransferObject\Award;
+
+/**
+ * @extends AbstractCompareService<Award[]>
+ */
+class AwardCompareService extends AbstractCompareService
+{
+    protected function parseFile(string $file)
+    {
+        return $this->serializer->deserialize(file_get_contents($file), Award::class . '[]', 'json');
+    }
+
+    public function compare($object1, $object2): void
+    {
+        $awards1Indexed = [];
+        foreach ($object1 as $award) {
+            $awards1Indexed[$award->id] = $award;
+        }
+
+        $awards2Indexed = [];
+        foreach ($object2 as $award) {
+            $awards2Indexed[$award->id] = $award;
+        }
+
+        foreach ($awards1Indexed as $awardId => $award) {
+            if (!isset($awards2Indexed[$awardId])) {
+                if (!$award->teamIds) {
+                    $this->addMessage(MessageType::INFO, sprintf('Award "%s" not found in second file, but has no team ID\'s in first file', $awardId));
+                } else {
+                    $this->addMessage(MessageType::ERROR, sprintf('Award "%s" not found in second file', $awardId));
+                }
+            } else {
+                $award2 = $awards2Indexed[$awardId];
+                if ($award->citation !== $award2->citation) {
+                    $this->addMessage(MessageType::WARNING, sprintf('Award "%s" has different citation', $awardId), $award->citation, $award2->citation);
+                }
+                $award1TeamIds = $award->teamIds;
+                sort($award1TeamIds);
+                $award2TeamIds = $award2->teamIds;
+                sort($award2TeamIds);
+                if ($award1TeamIds !== $award2TeamIds) {
+                    $this->addMessage(MessageType::ERROR, sprintf('Award "%s" has different team ID\'s', $awardId), implode(', ', $award->teamIds), implode(', ', $award2->teamIds));
+                }
+            }
+        }
+
+        foreach ($awards2Indexed as $awardId => $award) {
+            if (!isset($awards1Indexed[$awardId])) {
+                if (!$award->teamIds) {
+                    $this->addMessage(MessageType::INFO, sprintf('Award "%s" not found in first file, but has no team ID\'s in second file', $awardId));
+                } else {
+                    $this->addMessage(MessageType::ERROR, sprintf('Award "%s" not found in first file', $awardId));
+                }
+            }
+        }
+    }
+}
diff --git a/webapp/src/Service/Compare/Message.php b/webapp/src/Service/Compare/Message.php
new file mode 100644
index 0000000000..cd198a3436
--- /dev/null
+++ b/webapp/src/Service/Compare/Message.php
@@ -0,0 +1,13 @@
+<?php declare(strict_types=1);
+
+namespace App\Service\Compare;
+
+class Message
+{
+    public function __construct(
+        public readonly MessageType $type,
+        public readonly string $message,
+        public readonly ?string $source = null,
+        public readonly ?string $target = null,
+    ) {}
+}
diff --git a/webapp/src/Service/Compare/MessageType.php b/webapp/src/Service/Compare/MessageType.php
new file mode 100644
index 0000000000..84271c9bd9
--- /dev/null
+++ b/webapp/src/Service/Compare/MessageType.php
@@ -0,0 +1,10 @@
+<?php declare(strict_types=1);
+
+namespace App\Service\Compare;
+
+enum MessageType: string
+{
+    case INFO = 'info';
+    case WARNING = 'warning';
+    case ERROR = 'error';
+}
diff --git a/webapp/src/Service/Compare/ResultsCompareService.php b/webapp/src/Service/Compare/ResultsCompareService.php
new file mode 100644
index 0000000000..38ccc871dc
--- /dev/null
+++ b/webapp/src/Service/Compare/ResultsCompareService.php
@@ -0,0 +1,85 @@
+<?php declare(strict_types=1);
+
+namespace App\Service\Compare;
+
+use App\DataTransferObject\ResultRow;
+use Symfony\Component\Serializer\Encoder\CsvEncoder;
+
+/**
+ * @extends AbstractCompareService<ResultRow[]>
+ */
+class ResultsCompareService extends AbstractCompareService
+{
+    protected function parseFile(string $file)
+    {
+        $resultsContents = file_get_contents($file);
+        if (!str_starts_with($resultsContents, "results\t1")) {
+            $this->addMessage(MessageType::ERROR, sprintf("File \"%s\" does not start with \"results\t1\"", $file));
+            return null;
+        }
+
+        $resultsContents = substr($resultsContents, strpos($resultsContents, "\n") + 1);
+
+        // Prefix file with a fake header, so we can deserialize them
+        $resultsContents = "team_id\trank\taward\tnum_solved\ttotal_time\ttime_of_last_submission\tgroup_winner\n" . $resultsContents;
+
+        $results = $this->serializer->deserialize($resultsContents, ResultRow::class . '[]', 'csv', [
+            CsvEncoder::DELIMITER_KEY => "\t",
+        ]);
+
+        // Sort results: first by num_solved, then by total_time
+        usort($results, fn(
+            ResultRow $a,
+            ResultRow $b
+        ) => $a->numSolved === $b->numSolved ? $a->totalTime <=> $b->totalTime : $b->numSolved <=> $a->numSolved);
+
+        return $results;
+    }
+
+    public function compare($object1, $object2): void
+    {
+        /** @var array<string,ResultRow> $results1Indexed */
+        $results1Indexed = [];
+        foreach ($object1 as $result) {
+            $results1Indexed[$result->teamId] = $result;
+        }
+
+        /** @var array<string,ResultRow> $results2Indexed */
+        $results2Indexed = [];
+        foreach ($object2 as $result) {
+            $results2Indexed[$result->teamId] = $result;
+        }
+
+        foreach ($object1 as $result) {
+            if (!isset($results2Indexed[$result->teamId])) {
+                $this->addMessage(MessageType::ERROR, sprintf('Team "%s" not found in second file', $result->teamId));
+            } else {
+                $result2 = $results2Indexed[$result->teamId];
+                if ($result->rank !== $result2->rank) {
+                    $this->addMessage(MessageType::ERROR, sprintf('Team "%s" has different rank', $result->teamId), (string)$result->rank, (string)$result2->rank);
+                }
+                if ($result->award !== $result2->award) {
+                    $this->addMessage(MessageType::ERROR, sprintf('Team "%s" has different award', $result->teamId), $result->award, $result2->award);
+                }
+                if ($result->numSolved !== $result2->numSolved) {
+                    $this->addMessage(MessageType::ERROR, sprintf('Team "%s" has different num solved', $result->teamId), (string)$result->numSolved, (string)$result2->numSolved);
+                }
+                if ($result->totalTime !== $result2->totalTime) {
+                    $this->addMessage(MessageType::ERROR, sprintf('Team "%s" has different total time', $result->teamId), (string)$result->totalTime, (string)$result2->totalTime);
+                }
+                if ($result->timeOfLastSubmission !== $result2->timeOfLastSubmission) {
+                    $this->addMessage(MessageType::ERROR, sprintf('Team "%s" has different last time', $result->teamId), (string)$result->timeOfLastSubmission, (string)$result2->timeOfLastSubmission);
+                }
+                if ($result->groupWinner !== $result2->groupWinner) {
+                    $this->addMessage(MessageType::WARNING, sprintf('Team "%s" has different group winner', $result->teamId), (string)$result->groupWinner, (string)$result2->groupWinner);
+                }
+            }
+        }
+
+        foreach ($object2 as $result) {
+            if (!isset($results1Indexed[$result->teamId])) {
+                $this->addMessage(MessageType::ERROR, sprintf('Team "%s" not found in first file', $result->teamId));
+            }
+        }
+    }
+}
diff --git a/webapp/src/Service/Compare/ScoreboardCompareService.php b/webapp/src/Service/Compare/ScoreboardCompareService.php
new file mode 100644
index 0000000000..1f05941ae9
--- /dev/null
+++ b/webapp/src/Service/Compare/ScoreboardCompareService.php
@@ -0,0 +1,134 @@
+<?php declare(strict_types=1);
+
+namespace App\Service\Compare;
+
+use App\DataTransferObject\Scoreboard\Problem;
+use App\DataTransferObject\Scoreboard\Scoreboard;
+
+/**
+ * @extends AbstractCompareService<Scoreboard>
+ */
+class ScoreboardCompareService extends AbstractCompareService
+{
+    protected function parseFile(string $file)
+    {
+        return $this->serializer->deserialize(file_get_contents($file), Scoreboard::class, 'json', ['disable_type_enforcement' => true]);
+    }
+
+    public function compare($object1, $object2): void
+    {
+        if ($object1->eventId !== $object2->eventId) {
+            $this->addMessage(MessageType::INFO, 'Event ID does not match', $object1->eventId, $object2->eventId);
+        }
+
+        if ($object1->time !== $object2->time) {
+            $this->addMessage(MessageType::INFO, 'Time does not match', $object1->time, $object2->time);
+        }
+
+        if ($object1->contestTime !== $object2->contestTime) {
+            $this->addMessage(MessageType::INFO, 'Contest time does not match', $object1->contestTime, $object2->contestTime);
+        }
+
+        if (($object1->state->started ?? '') !== ($object2->state->started ?? '')) {
+            $this->addMessage(MessageType::WARNING, 'State started does not match', $object1->state->started, $object2->state->started);
+        }
+
+        if (($object1->state->ended ?? '') !== ($object2->state->ended ?? '')) {
+            $this->addMessage(MessageType::WARNING, 'State ended does not match', $object1->state->ended, $object2->state->ended);
+        }
+
+        if (($object1->state->frozen ?? '') !== ($object2->state->frozen ?? '')) {
+            $this->addMessage(MessageType::WARNING, 'State frozen does not match', $object1->state->frozen, $object2->state->frozen);
+        }
+
+        if (($object1->state->thawed ?? '') !== ($object2->state->thawed ?? '')) {
+            $this->addMessage(MessageType::WARNING, 'State thawed does not match', $object1->state->thawed, $object2->state->thawed);
+        }
+
+        if (($object1->state->finalized ?? '') !== ($object2->state->finalized ?? '')) {
+            $this->addMessage(MessageType::WARNING, 'State finalized does not match', $object1->state->finalized, $object2->state->finalized);
+        }
+
+        if (($object1->state->endOfUpdates ?? '') !== ($object2->state->endOfUpdates ?? '')) {
+            $this->addMessage(MessageType::WARNING, 'State end of updates does not match', $object1->state->endOfUpdates, $object2->state->endOfUpdates);
+        }
+
+        if (count($object1->rows) !== count($object2->rows)) {
+            $this->addMessage(MessageType::ERROR, 'Number of rows does not match', (string)count($object1->rows), (string)count($object2->rows));
+        }
+
+        foreach ($object1->rows as $index => $row) {
+            if ($row->teamId !== $object2->rows[$index]->teamId) {
+                $this->addMessage(MessageType::ERROR, sprintf('Row %d: team ID does not match', $index), $row->teamId, $object2->rows[$index]->teamId);
+            }
+
+            if ($row->rank !== $object2->rows[$index]->rank) {
+                $this->addMessage(MessageType::ERROR, sprintf('Row %d: rank does not match', $index), (string)$row->rank, (string)$object2->rows[$index]->rank);
+            }
+
+            if ($row->score->numSolved !== $object2->rows[$index]->score->numSolved) {
+                $this->addMessage(MessageType::ERROR, sprintf('Row %d: num solved does not match', $index), (string)$row->score->numSolved, (string)$object2->rows[$index]->score->numSolved);
+            }
+
+            if ($row->score->totalTime !== $object2->rows[$index]->score->totalTime) {
+                $this->addMessage(MessageType::ERROR, sprintf('Row %d: total time does not match', $index), (string)$row->score->totalTime, (string)$object2->rows[$index]->score->totalTime);
+            }
+
+            foreach ($row->problems as $problem) {
+                /** @var Problem|null $problemForSecond */
+                $problemForSecond = null;
+
+                foreach ($object2->rows[$index]->problems as $problem2) {
+                    // PC^2 uses different problem ID's. For now also match on `Id = {problemId}-{digits}`
+                    if ($problem->problemId === $problem2->problemId) {
+                        $problemForSecond = $problem2;
+                        break;
+                    } elseif (preg_match('/^Id = ' . preg_quote($problem->problemId, '/') . '-+\d+$/', $problem2->problemId)) {
+                        $problemForSecond = $problem2;
+                        break;
+                    }
+                }
+
+                if ($problemForSecond === null && $problem->solved) {
+                    $this->addMessage(MessageType::ERROR, sprintf('Row %d: Problem %s solved in first file, but not found in second file', $index, $problem->problemId));
+                } elseif ($problemForSecond !== null && $problem->solved !== $problemForSecond->solved) {
+                    $this->addMessage(MessageType::ERROR, sprintf('Row %d: Problem %s solved does not match', $index, $problem->problemId), (string)$problem->solved, (string)$problemForSecond->solved);
+                }
+
+                if ($problemForSecond) {
+                    if ($problem->numJudged !== $problemForSecond->numJudged) {
+                        $this->addMessage(MessageType::ERROR, sprintf('Row %d: Problem %s num judged does not match', $index, $problem->problemId), (string)$problem->numJudged, (string)$problemForSecond->numJudged);
+                    }
+
+                    if ($problem->numPending !== $problemForSecond->numPending) {
+                        $this->addMessage(MessageType::ERROR, sprintf('Row %d: Problem %s num pending does not match', $index, $problem->problemId), (string)$problem->numPending, (string)$problemForSecond->numPending);
+                    }
+
+                    if ($problem->time !== $problemForSecond->time) {
+                        // This is an info message for now, since PC^2 doesn't expose time info
+                        $this->addMessage(MessageType::INFO, sprintf('Row %d: Problem %s time does not match', $index, $problem->problemId), (string)$problem->time, (string)$problemForSecond->time);
+                    }
+                }
+            }
+
+            foreach ($object2->rows[$index]->problems as $problem2) {
+                $problemForFirst = null;
+
+                foreach ($row->problems as $problem) {
+                    // PC^2 uses different problem ID's. For now also match on `Id = {problemId}-{digits}`
+                    if ($problem->problemId === $problem2->problemId) {
+                        $problemForFirst = $problem;
+                        break;
+                    } elseif (preg_match('/^Id = ' . preg_quote($problem->problemId, '/') . '-+\d+$/', $problem2->problemId)) {
+                        $problemForFirst = $problem;
+                        break;
+                    }
+                }
+
+                if ($problemForFirst === null && $problem2->solved) {
+                    $this->addMessage(MessageType::ERROR, sprintf('Row %d: Problem %s solved in second file, but not found in first file', $index, $problem2->problemId));
+                }
+            }
+        }
+    }
+}
diff --git a/webapp/tests/Unit/Service/Compare/AwardCompareServiceTest.php b/webapp/tests/Unit/Service/Compare/AwardCompareServiceTest.php
new file mode 100644
index 0000000000..55f7b03277
--- /dev/null
+++ b/webapp/tests/Unit/Service/Compare/AwardCompareServiceTest.php
@@ -0,0 +1,67 @@
+<?php declare(strict_types=1);
+
+namespace App\Tests\Unit\Service\Compare;
+
+use App\DataTransferObject\Award;
+use App\Service\Compare\AwardCompareService;
+use App\Service\Compare\Message;
+use App\Service\Compare\MessageType;
+use Generator;
+use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;
+use Symfony\Component\Serializer\SerializerInterface;
+
+class AwardCompareServiceTest extends KernelTestCase
+{
+    /**
+     * @param Award[]   $awards1
+     * @param Award[]   $awards2
+     * @param Message[] $expectedMessages
+     *
+     * @dataProvider provideCompare
+     */
+    public function testCompare(array $awards1, array $awards2, array $expectedMessages): void
+    {
+        $serializer = $this->createMock(SerializerInterface::class);
+        $compareService = new AwardCompareService($serializer);
+
+        $compareService->compare($awards1, $awards2);
+        $messages = $compareService->getMessages();
+
+        self::assertEquals($expectedMessages, $messages);
+    }
+
+    public function provideCompare(): Generator
+    {
+        yield [[], [], []];
+        yield [
+            [new Award('award1', null, [])],
+            [],
+            [new Message(MessageType::INFO, 'Award "award1" not found in second file, but has no team ID\'s in first file', null, null)],
+        ];
+        yield [
+            [],
+            [new Award('award2', null, [])],
+            [new Message(MessageType::INFO, 'Award "award2" not found in first file, but has no team ID\'s in second file', null, null)],
+        ];
+        yield [
+            [new Award('award3', null, ["1", "2", "3"])],
+            [],
+            [new Message(MessageType::ERROR, 'Award "award3" not found in second file', null, null)],
+        ];
+        yield [
+            [],
+            [new Award('award4', null, ["1", "2", "3"])],
+            [new Message(MessageType::ERROR, 'Award "award4" not found in first file', null, null)],
+        ];
+        yield [
+            [new Award('award1', 'citation1', [])],
+            [new Award('award1', 'citation2', [])],
+            [new Message(MessageType::WARNING, 'Award "award1" has different citation', 'citation1', 'citation2')],
+        ];
+        yield [
+            [new Award('award1', 'citation1', ["1", "2"])],
+            [new Award('award1', 'citation1', ["2", "3"])],
+            [new Message(MessageType::ERROR, 'Award "award1" has different team ID\'s', '1, 2', '2, 3')],
+        ];
+    }
+}
diff --git a/webapp/tests/Unit/Service/Compare/ResultsCompareServiceTest.php b/webapp/tests/Unit/Service/Compare/ResultsCompareServiceTest.php
new file mode 100644
index 0000000000..4c5124ef01
--- /dev/null
+++ b/webapp/tests/Unit/Service/Compare/ResultsCompareServiceTest.php
@@ -0,0 +1,77 @@
+<?php declare(strict_types=1);
+
+namespace App\Tests\Unit\Service\Compare;
+
+use App\DataTransferObject\ResultRow;
+use App\Service\Compare\Message;
+use App\Service\Compare\MessageType;
+use App\Service\Compare\ResultsCompareService;
+use Generator;
+use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;
+use Symfony\Component\Serializer\SerializerInterface;
+
+class ResultsCompareServiceTest extends KernelTestCase
+{
+    /**
+     * @param ResultRow[]  $results1
+     * @param ResultRow[]  $results2
+     * @param Message[] $expectedMessages
+     *
+     * @dataProvider provideCompare
+     */
+    public function testCompare(array $results1, array $results2, array $expectedMessages): void
+    {
+        $serializer = $this->createMock(SerializerInterface::class);
+        $compareService = new ResultsCompareService($serializer);
+
+        $compareService->compare($results1, $results2);
+        $messages = $compareService->getMessages();
+
+        self::assertEquals($expectedMessages, $messages);
+    }
+
+    public function provideCompare(): Generator
+    {
+        yield [[], [], []];
+        yield [
+            [new ResultRow('team1', 1, '', 0, 0, 0)],
+            [],
+            [new Message(MessageType::ERROR, 'Team "team1" not found in second file', null, null)],
+        ];
+        yield [
+            [],
+            [new ResultRow('team2', 1, '', 0, 0, 0)],
+            [new Message(MessageType::ERROR, 'Team "team2" not found in first file', null, null)],
+        ];
+        yield [
+            [new ResultRow('team3', 1, '', 0, 0, 0)],
+            [new ResultRow('team3', 2, '', 0, 0, 0)],
+            [new Message(MessageType::ERROR, 'Team "team3" has different rank', '1', '2')],
+        ];
+        yield [
+            [new ResultRow('team4', 1, 'award1', 0, 0, 0)],
+            [new ResultRow('team4', 1, 'award2', 0, 0, 0)],
+            [new Message(MessageType::ERROR, 'Team "team4" has different award', 'award1', 'award2')],
+        ];
+        yield [
+            [new ResultRow('team5', 1, 'award3', 1, 0, 0)],
+            [new ResultRow('team5', 1, 'award3', 2, 0, 0)],
+            [new Message(MessageType::ERROR, 'Team "team5" has different num solved', '1', '2')],
+        ];
+        yield [
+            [new ResultRow('team6', 1, 'award4', 1, 100, 0)],
+            [new ResultRow('team6', 1, 'award4', 1, 200, 0)],
+            [new Message(MessageType::ERROR, 'Team "team6" has different total time', '100', '200')],
+        ];
+        yield [
+            [new ResultRow('team7', 1, 'award4', 1, 100, 10)],
+            [new ResultRow('team7', 1, 'award4', 1, 100, 20)],
+            [new Message(MessageType::ERROR, 'Team "team7" has different last time', '10', '20')],
+        ];
+        yield [
+            [new ResultRow('team8', 1, 'award4', 1, 100, 10, 'winner1')],
+            [new ResultRow('team8', 1, 'award4', 1, 100, 10, 'winner2')],
+            [new Message(MessageType::WARNING, 'Team "team8" has different group winner', 'winner1', 'winner2')],
+        ];
+    }
+}
diff --git a/webapp/tests/Unit/Service/Compare/ScoreboardCompareServiceTest.php b/webapp/tests/Unit/Service/Compare/ScoreboardCompareServiceTest.php
new file mode 100644
index 0000000000..84879451e8
--- /dev/null
+++ b/webapp/tests/Unit/Service/Compare/ScoreboardCompareServiceTest.php
@@ -0,0 +1,188 @@
+<?php declare(strict_types=1);
+
+namespace App\Tests\Unit\Service\Compare;
+
+use App\DataTransferObject\ContestState;
+use App\DataTransferObject\Scoreboard\Problem;
+use App\DataTransferObject\Scoreboard\Row;
+use App\DataTransferObject\Scoreboard\Score;
+use App\DataTransferObject\Scoreboard\Scoreboard;
+use App\Service\Compare\Message;
+use App\Service\Compare\MessageType;
+use App\Service\Compare\ScoreboardCompareService;
+use Generator;
+use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;
+use Symfony\Component\Serializer\SerializerInterface;
+
+class ScoreboardCompareServiceTest extends KernelTestCase
+{
+    /**
+     * @param Message[] $expectedMessages
+     *
+     * @dataProvider provideCompare
+     */
+    public function testCompare(
+        Scoreboard $scoreboard1,
+        Scoreboard $scoreboard2,
+        array $expectedMessages
+    ): void {
+        $serializer = $this->createMock(SerializerInterface::class);
+        $compareService = new ScoreboardCompareService($serializer);
+
+        $compareService->compare($scoreboard1, $scoreboard2);
+        $messages = $compareService->getMessages();
+
+        self::assertEquals($expectedMessages, $messages);
+    }
+
+    public function provideCompare(): Generator
+    {
+        yield [new Scoreboard(), new Scoreboard(), []];
+        yield [
+            new Scoreboard('123'),
+            new Scoreboard('456'),
+            [new Message(MessageType::INFO, 'Event ID does not match', '123', '456')],
+        ];
+        yield [
+            new Scoreboard('123', '456'),
+            new Scoreboard('123', '123'),
+            [new Message(MessageType::INFO, 'Time does not match', '456', '123')],
+        ];
+        yield [
+            new Scoreboard('123', '456', '111'),
+            new Scoreboard('123', '456', '222'),
+            [new Message(MessageType::INFO, 'Contest time does not match', '111', '222')],
+        ];
+        yield [
+            new Scoreboard('123', '456', '111', new ContestState(started: '123')),
+            new Scoreboard('123', '456', '111', new ContestState(started: '456')),
+            [new Message(MessageType::WARNING, 'State started does not match', '123', '456')],
+        ];
+        yield [
+            new Scoreboard('123', '456', '111', new ContestState(ended: '123')),
+            new Scoreboard('123', '456', '111', new ContestState(ended: '456')),
+            [new Message(MessageType::WARNING, 'State ended does not match', '123', '456')],
+        ];
+        yield [
+            new Scoreboard('123', '456', '111', new ContestState(frozen: '123')),
+            new Scoreboard('123', '456', '111', new ContestState(frozen: '456')),
+            [new Message(MessageType::WARNING, 'State frozen does not match', '123', '456')],
+        ];
+        yield [
+            new Scoreboard('123', '456', '111', new ContestState(thawed: '123')),
+            new Scoreboard('123', '456', '111', new ContestState(thawed: '456')),
+            [new Message(MessageType::WARNING, 'State thawed does not match', '123', '456')],
+        ];
+        yield [
+            new Scoreboard('123', '456', '111', new ContestState(finalized: '123')),
+            new Scoreboard('123', '456', '111', new ContestState(finalized: '456')),
+            [new Message(MessageType::WARNING, 'State finalized does not match', '123', '456')],
+        ];
+        yield [
+            new Scoreboard('123', '456', '111', new ContestState(endOfUpdates: '123')),
+            new Scoreboard('123', '456', '111', new ContestState(endOfUpdates: '456')),
+            [new Message(MessageType::WARNING, 'State end of updates does not match', '123', '456')],
+        ];
+        yield [
+            new Scoreboard(rows: []),
+            new Scoreboard(rows: [new Row(1, '123', new Score(0), [])]),
+            [new Message(MessageType::ERROR, 'Number of rows does not match', '0', '1')],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(0), [])]),
+            new Scoreboard(rows: [new Row(1, '456', new Score(0), [])]),
+            [new Message(MessageType::ERROR, 'Row 0: team ID does not match', '123', '456')],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(0), [])]),
+            new Scoreboard(rows: [new Row(2, '123', new Score(0), [])]),
+            [new Message(MessageType::ERROR, 'Row 0: rank does not match', '1', '2')],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [])]),
+            new Scoreboard(rows: [new Row(1, '123', new Score(2), [])]),
+            [new Message(MessageType::ERROR, 'Row 0: num solved does not match', '1', '2')],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(1, 123), [])]),
+            new Scoreboard(rows: [new Row(1, '123', new Score(1, 456), [])]),
+            [new Message(MessageType::ERROR, 'Row 0: total time does not match', '123', '456')],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 0, true),
+            ])]),
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 0, true),
+            ])]),
+            [],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 0, true),
+            ])]),
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 0, false),
+            ])]),
+            [new Message(MessageType::ERROR, 'Row 0: Problem a solved does not match', '1', '')],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 0, true),
+            ])]),
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [])]),
+            [new Message(MessageType::ERROR, 'Row 0: Problem a solved in first file, but not found in second file')],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [])]),
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 0, true),
+            ])]),
+            [new Message(MessageType::ERROR, 'Row 0: Problem a solved in second file, but not found in first file')],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 0, true),
+            ])]),
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 2, 0, true),
+            ])]),
+            [new Message(MessageType::ERROR, 'Row 0: Problem a num judged does not match', '1', '2')],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 3, true),
+            ])]),
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 4, true),
+            ])]),
+            [new Message(MessageType::ERROR, 'Row 0: Problem a num pending does not match', '3', '4')],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 3, true, 123),
+            ])]),
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 3, true, 456),
+            ])]),
+            [new Message(MessageType::INFO, 'Row 0: Problem a time does not match', '123', '456')],
+        ];
+        // PC^2 uses different problem ID's. Also test on `Id = {problemId}-{digits}`
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'a', 1, 0, true),
+            ])]),
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'Id = a-123', 1, 0, true),
+            ])]),
+            [],
+        ];
+        yield [
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [])]),
+            new Scoreboard(rows: [new Row(1, '123', new Score(1), [
+                new Problem('A', 'Id = a-123', 1, 0, true),
+            ])]),
+            [new Message(MessageType::ERROR, 'Row 0: Problem Id = a-123 solved in second file, but not found in first file')],
+        ];
+    }
+}