What is the maximum size of a single step output set via $GITHUB_OUTPUT?
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Short Explanation and Infographic
The 1 MB limit applies to the GITHUB_OUTPUT file as a whole — very large data should go in artifacts, not outputs.
Full explanation below image
Full Explanation
The $GITHUB_OUTPUT file has a total file size limit of 1 MB across all outputs written during a step. Individual output values don't have separate per-output limits, but the combined file content must stay under 1 MB. For large data (build manifests, JSON configurations, file lists), use artifacts or the job summary (GITHUB_STEP_SUMMARY) instead. Step outputs are meant for lightweight string values like version numbers, boolean flags, or short identifiers. Values that exceed sensible sizes should be written to files and uploaded as artifacts.