Fix: Prevent font-size adjustments on iOS after orientation change #3648

maxchang3 · 2026-01-05T17:18:32Z

Description

This PR adds text-size-adjust rules on the html element in reset.css to prevent platform-specific, inconsistent font scaling on iOS WebKit when the device orientation changes.

Problem

On iOS Safari (WebKit), rotating to landscape can trigger text autosizing that causes unwanted font-size adjustments across various UI elements, and the sizes may not revert when rotating back.

Solution

Apply -webkit-text-size-adjust: 100% and text-size-adjust: 100% on the html element to keep sizes consistent across orientation changes without affecting user zoom or accessibility settings.

This approach is widely used in mainstream CSS resets, including: normalize.css, tailwindcss/preflight, and modern-normalize.

This feature was originally introduced by Apple and is non-standard in origin¹. Although text-size-adjust is now standardized, regarding Safari, only the mobile version² supports the prefixed -webkit-text-size-adjust, while Chromium supports the unprefixed version³⁴.

Testing

Tested on iOS Safari (iOS 26.1, iPhone 15 Pro). Further testing can be done via the deploy preview provided by this PR.

Before and After Video

Before	After
before.mp4	after.mp4

Background reading:

Your CSS reset needs text-size-adjust (probably)

changeset-bot · 2026-01-05T17:18:36Z

🦋 Changeset detected

Latest commit: 6abbf42

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@astrojs/starlight	Patch

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netlify · 2026-01-05T17:18:37Z

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astrobot-houston · 2026-01-05T17:18:59Z

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randomguy-2650

I tested this and it seems good to go!

I left a comment regarding about the wording of the changeset but that’s it.

.changeset/popular-rules-turn.md

Co-authored-by: randomguy-2650 <[email protected]>

HiDeoo · 2026-01-06T18:38:18Z

Thanks for opening a PR, really appreciated 🙌

I think we'll take a look at it in our weekly Discord Talking & Doc'ing event that we use to publicly handle various aspects of the project. You are of course welcome to join us live if you're interested and available!

For such changes that can have a visual impact, and may differ between different users devices or browsers, it's a great way to have many eyes on it and get feedback so I think we will use this opportunity to test the PR on many devices (even Android ones to make sure it does not have any impact there).

sarah11918 · 2026-01-08T14:50:08Z

Tested deploy preview on S23 Ultra and 14" Android mobile Chrome and this PR doesn't break anything there! Still works on Android for me!

ArmandPhilippot · 2026-01-08T14:50:39Z

Tested on Android 15 with Firefox 146.0.1, no issues introduced for me! Great job 🙌🏽

trueberryless

Thanks for the fix!
I tested on an Android device with Google Chrome and Firefox too and it seems to not have broken anything ✅

delucis

Thanks for the PR and the very thorough documentation and research — appreciate it @maxchang3!

And thanks to everyone who tested this on Talking & Doc’ing! Great to get those extra eyes and testing on a change like this 💖

This PR contains the following updates: | Package | Change | [Age](https://docs.renovatebot.com/merge-confidence/) | [Confidence](https://docs.renovatebot.com/merge-confidence/) | |---|---|---|---| | [@astrojs/starlight](https://starlight.astro.build) ([source](https://github.com/withastro/starlight/tree/HEAD/packages/starlight)) | [`0.37.2` → `0.37.3`](https://renovatebot.com/diffs/npm/@astrojs%2fstarlight/0.37.2/0.37.3) | ![age](https://developer.mend.io/api/mc/badges/age/npm/@astrojs%2fstarlight/0.37.3?slim=true) | ![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/@astrojs%2fstarlight/0.37.2/0.37.3?slim=true) | --- ### Release Notes <details> <summary>withastro/starlight (@astrojs/starlight)</summary> ### [`v0.37.3`](https://github.com/withastro/starlight/blob/HEAD/packages/starlight/CHANGELOG.md#0373) [Compare Source](https://github.com/withastro/starlight/compare/@astrojs/[email protected]...@astrojs/[email protected]) ##### Patch Changes - [#3648](withastro/starlight#3648) [`292666c`](withastro/starlight@292666c) Thanks [@maxchang3](https://github.com/maxchang3)! - Prevents unwanted font size adjustments on iOS after orientation changes. </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied. ♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox. 🔕 **Ignore**: Close this PR and you won't be reminded about this update again. --- - [ ] If you want to rebase/retry this PR, check this box --- This PR has been generated by [Renovate Bot](https://github.com/renovatebot/renovate).  Co-authored-by: Renovate Bot <[email protected]> Co-committed-by: Renovate Bot <[email protected]>

maxchang3 added 2 commits January 6, 2026 01:00

Fix: Prevent font-size adjustments on iOS after orientation change

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Add changeset

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github-actions bot added the 🌟 core Changes to Starlight’s main package label Jan 5, 2026

maxchang3 mentioned this pull request Jan 5, 2026

Font size increases when orientation switches to horizontal #3615

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randomguy-2650 approved these changes Jan 5, 2026

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.changeset/popular-rules-turn.md Outdated Show resolved Hide resolved

Shorten and refine changelog

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Co-authored-by: randomguy-2650 <[email protected]>

sarah11918 approved these changes Jan 8, 2026

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trueberryless approved these changes Jan 8, 2026

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Merge branch 'main' into fix/font-boosting

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mohmed1503-stack approved these changes Jan 12, 2026

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delucis approved these changes Jan 12, 2026

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delucis added 🌟 patch Change that triggers a patch release ✅ approved Pull requests that have been approved and are ready to merge when next cutting a release labels Jan 12, 2026

delucis merged commit 292666c into withastro:main Jan 12, 2026
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astrobot-houston mentioned this pull request Jan 12, 2026

[ci] release #3654

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