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Jul 16, 2025
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Rewrite Workers Memory Limits docs #19049

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Rewrite Workers Memory Limits docs
irvinebroque Jan 7, 2025
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Update src/content/docs/workers/platform/limits.mdx
irvinebroque Jan 7, 2025
317e00a
Update src/content/docs/workers/platform/limits.mdx
southpolesteve Jan 7, 2025
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Update src/content/docs/workers/platform/limits.mdx
irvinebroque Jan 10, 2025
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12 changes: 7 additions & 5 deletions src/content/docs/workers/platform/limits.mdx
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Expand Up @@ -148,17 +148,19 @@ Routes in fail closed mode will display a Cloudflare `1027` error page to visito

## Memory

Only one Workers instance runs on each of the many global Cloudflare global network servers. Each Workers instance can consume up to 128 MB of memory. Use [global variables](/workers/runtime-apis/web-standards/) to persist data between requests on individual nodes. Note however, that nodes are occasionally evicted from memory.
Each [isolate](/workers/reference/how-workers-works/#isolates) of your Worker's code runs in can consume up to 128 MB of memory. This includes both memory used by the JavaScript heap, and memory explicitly allocated in [WebAssembly](/workers/runtime-apis/webassembly/). Note that this limit is per-isolate, not per-invocation of your Worker. A single isolate can handle many concurrent requests.

If a Worker processes a request that pushes the Worker over the 128 MB limit, the Cloudflare Workers runtime may cancel one or more requests. To view these errors, as well as CPU limit overages:
When an isolate running your Worker exceeds 128 MB of memory, the Workers runtime handles this gracefully instead of failing immediately. It allows in-flight requests to complete while simultaneously creating a new isolate for your Worker for new requests. While this approach typically allows in-flight requests to complete, during periods of extremely high load, some incoming requests may be cancelled to maintain system stability.

To view out-of-memory errors (OOM), as well as CPU limit overages:

1. Log in to the [Cloudflare dashboard](https://dash.cloudflare.com) and select your account.
2. Select **Workers & Pages** and in **Overview**, select the Worker you would like to investigate.
3. Under **Metrics**, select **Errors** > **Invocation Statuses** and examine **Exceeded Memory**.

Use the [TransformStream API](/workers/runtime-apis/streams/transformstream/) to stream responses if you are concerned about memory usage. This avoids loading an entire response into memory.
To avoid exceeding memory limits, where possible you should avoid buffering large objects or responses in memory, and instead use streaming APIs such as [`TransformStream`](/workers/runtime-apis/streams/transformstream/) or [`node:stream`](/workers/runtime-apis/nodejs/streams/) to stream responses. Manipulating streams allows you to avoid buffering entire responses in memory.

Using DevTools locally can help identify memory leaks in your code. See the [memory profiling with DevTools documentation](/workers/observability/dev-tools/memory-usage/) to learn more.
You can also use Chrome DevTools in local development to identify memory leaks in your code. See the [memory profiling with DevTools documentation](/workers/observability/dev-tools/memory-usage/) to learn more.

---

Expand Down Expand Up @@ -334,4 +336,4 @@ Review other developer platform resource limits.

- [KV limits](/kv/platform/limits/)
- [Durable Object limits](/durable-objects/platform/limits/)
- [Queues limits](/queues/platform/limits/)
- [Queues limits](/queues/platform/limits/)
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