GitHub Username Availability Checker

A small Chrome extension for checking whether GitHub username candidates are available for your account. From GitHub's account settings page, paste a list of candidates; the extension uses GitHub's own rename validator without submitting a username change.

Checking github.com/USERNAME is not reliable for this: GitHub can return a 404 for a username that is still reserved or otherwise unavailable to rename into. This extension checks the validator GitHub uses in the account rename flow instead.

Use it locally

1. Open chrome://extensions.
2. Enable Developer mode.
3. Click Load unpacked and select this repository folder.
4. In GitHub, open Settings → Account.
5. Click the green Check usernames button in the bottom-right corner of the page.
6. Paste up to 150 candidates into the extension panel, then click Check candidates.

If the extension says it cannot find GitHub's validator:

1. Under Change username, click Change username.
2. In GitHub's warning dialog, click I understand, let’s change my username.
3. Close GitHub's rename dialog. Do not enter a username or click Change my username.
4. Open the extension again and retry the check.

Privacy and limitations

• Candidates are checked directly with GitHub. The extension does not send them to a separate service or store them.
• It relies on GitHub's internal username-change check, which may stop working if GitHub updates its settings page.
• HTTP 200 results are marked available, and HTTP 422 results are marked unavailable. Network failures and other HTTP statuses are marked unknown.
• Checks stop after three consecutive unknown results to avoid repeatedly calling a failing endpoint.
• Checks run at roughly one candidate every 900 ms. Closing the checker or navigating away stops the current batch, and results can be downloaded as CSV.