[WebExtensions] Chrome 150 plans to limit alarm name lengths

[bershanskiy]

Description

Add note stating upcoming limit for extension alarm names in Google Chrome 150.

Motivation

Chrome 148 introduced a console warning for alarm names longer than 1024 bytes.[1] Safari devs believe "1024 is a good limit".[2] Firefox will likely "take a wait and see approach".[3]

Additional details

Sources:
[1] chromium/chromium@432c30e
[2] w3c/webextensions#935 (comment)
[3] https://github.com/w3c/webextensions/blob/main/_minutes/2026-03-12-wecg.md

Related issues and pull requests

w3c/webextensions#422

[github-actions]

Preview URLs (1 page)

• /en-US/docs/Mozilla/Add-ons/WebExtensions/API/alarms/create

External URLs (1)

URL: /en-US/docs/Mozilla/Add-ons/WebExtensions/API/alarms/create
Title: alarms.create()

• https://github.com/w3c/webextensions/issues/935 (1 time) (Note! This may be a new URL 👀)

(comment last updated: 2026-04-26 19:07:53)

[rebloor]

@bershanskiy could you also add a note to the BCD?

Suggested change

	From Chrome 150, alarms with names longer than 1024 bytes are rejected. This limit may be implemented on other browsers. See [Proposal: Limits on lengths of strings passed to WebExtension APIs](https://github.com/w3c/webextensions/issues/935) for more information.

[bershanskiy]

@oliverdunk Courtesy ping in case you would like to review this change.

[rebloor]

@bershanskiy Normally, we just add a note under the Chrome entry for alarm.create, along the lines of

…
            "support": {
              "chrome": {
                "version_added": "22",
                "notes": [
                  "From Chrome 117, alarms are limited to 500 per extension.",
                  "From Chrome 150, alarm names are limited to 1024 bytes."
                ]
              },
…

[oliverdunk]

@oliverdunk Courtesy ping in case you would like to review this change.

This SGTM. No strong feelings on the wording or where this is noted.

[bershanskiy]

Normally, we just add a note under the Chrome entry for alarm.create

I updated mdn/browser-compat-data#29521 accordingly (updated commit, commit message, and force-pushed). Please let me know if I need to do anything else.

[rebloor]

Thanks @bershanskiy everything looks good.