The GitHub outage explained: What happened, who was affected, and how long did it last?

A lengthy GitHub outage that saw users struggle to access core services has been resolved, according to Microsoft, but what happened?

The incident first came to GitHub’s attention at around 1:40pm UTC yesterday, when the company said it was investigating reports of impacted performance for some services.

It proceeded to report problems with API Requests, Actions, Webhooks, Pull Requests, Issues, and GitHub Copilot.

"We are experiencing high error rates around 20% for web experiences and api traffic. Archive downloads and raw repository content downloads are experiencing an approximate 50% error rate," the company reported about an hour into the affair.

"SAML and OIDC authentication, SCIM, and Team Sync are also impacted. Investigations are on-going and we will continue to provide updates as we discover more information."

By 4.40pm, the firm said it had identified the problematic component and had taken corrective action – although error rates were still slightly up.

“We are still seeing residual impact in the form of sporadic authentication failures. We are continuing to apply additional mitigations and investigate the remaining impact,” GitHub said.

Full GitHub outage analysis pending

At one point, Downdetector was reporting nearly 3,000 outage reports, although the incident was finally resolved by 9.15pm.

Exact details on the cause of the incident are yet to be revealed. However, GitHub promised that a “detailed root cause analysis will be shared as soon as it is available”.

GitHub demand surging

GitHub is one of the world's largest software development platforms, with 225 million users, but has seen its infrastructure pushed to the limit by the boom in AI-driven coding.

Last October, it started work to boost capacity by ten times before realizing in February that a 30-fold increase would be required.

In an April blog post detailing the strain placed on the firm, CTO Vlad Fedorov said agentic workflows have "accelerated sharply” in recent months.

“By nearly every measure, the direction is already clear: repository creation, pull request activity, API usage, automation, and large-repository workloads are all growing quickly," Fedorov wrote.

He said GitHub planned to deal with availability first, then capacity, and then new features.

"We are reducing unnecessary work, improving caching, isolating critical services, removing single points of failure, and moving performance-sensitive paths into systems designed for these workloads," Fedorov said.

Repeated outages

Notably, it appears the company wasn't able to carry out this work fast enough, with eight further outages last month. This included a lengthy GitHub Actions outage that the company described as 'unacceptable'.

The company attributed this to the fact that the GitHub Actions service at the core of the incident was still fully running in its data centers, and promised to accelerate its move of GitHub Actions to Azure.

Here, the company noted, it will have more headroom and capabilities to absorb sharp spikes in activity.

"GitHub is on track to see a 1,400% increase in commit volume from 2025 to 2026, with most of the increase coming from AI tooling," commented Jamie Beckland, chief product officer at APIContext.

"Every technology team depends on platforms that are being reshaped by new demand from AI. Which means every technology team now has an AI infrastructure problem. Technology teams need independent monitoring of the third-party services sitting in their delivery path so they know whether problems affect developers, pipelines, and customers."

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