# Documentation sites with a custom domain returned a 404 error

- Provider: [GitBook](https://down.guide/providers/gitbook)
- Confidence: Confirmed
- Impact: Partial outage
- lasted 0m
- started 2026-03-06 16:56 UTC
- GitBook states the impact was 2026-03-06 14:36 to 14:43 UTC (7m)
- id: DWN-1a9c8bee0b
- Official page: https://www.gitbookstatus.com/incidents/01KK219E7DFDQZ9TYYQ7BGMFGA

## Root cause
> The issue was caused by a problem introduced by an upstream provider that affected our deployment.

Category: Deploy or config change. [Postmortem](https://www.gitbookstatus.com/incidents/01KK219E7DFDQZ9TYYQ7BGMFGA)

## Updates from GitBook
### 2026-03-06 14:36 UTC: resolved
Between 14:36 and 14:43 UTC, all GitBook documentation sites using a custom domain were returning a 404 "Not Found" error, making documentation unavailable to users. The issue was caused by a problem introduced by an upstream provider that affected our deployment. The incident was resolved by rolling back the deployment, after which all sites were confirmed to be fully operational.

From the builder: does your app depend on GitBook? [Sazabi](https://www.sazabi.com/?utm_source=down-guide&utm_medium=markdown&utm_content=gitbook) detects problems in your own logs without hand-written monitors, and you can ask it in plain language which errors mention GitBook.

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