Blender Auto Save Timer Limits During Playback and Long Renders

Direct Answer

The Auto Save timer does not pause during playback or rendering. Instead, the timer continues to fire on real‑time intervals, but the actual write operation runs as a modal operator that only executes when Blender’s event loop is idle. Consequently, any pending Auto Save is deferred until playback stops or the render yields control back to the main loop. Long‑running operations such as a full animation render behave the same way: the save occurs after the render finishes or at a yield point, not during active frame evaluation.

Confirmed Facts

• Auto Save interval is configurable in Preferences > Save & Load.
• Writes are saved to the system temporary directory and can be recovered via File > Recover > Auto Save.
• The feature has existed since Blender 2.80 with no documented changes to its timer logic in release notes.

Likely Explanation

Blender’s event loop processes modal operators (including the Auto Save write) only when it is not busy evaluating frames, scrubbing the timeline, or executing a render. The timer itself is not suspended; it simply queues a save request that waits for the next idle pass. There is no evidence that intervals are skipped or that the timer resets. The deferral boundary is the next iteration of the main loop where no modal operator holds control—typically after playback stops or when a render engine yields (e.g., between tiles or frames).

Cautions

• If Blender crashes while busy (playback, scrubbing, or mid‑render), any deferred Auto Save will not have been written, potentially losing work since the last successful save.
• The deferral is invisible in the UI; users may assume a save occurred during playback when it actually happened afterward.
• The exact yield points during rendering depend on the render engine and version, so behavior may vary.

Verification Steps

1. In Preferences > Save & Load, set Auto Save to a short interval (e.g., 5 seconds).
2. Start timeline playback or scrubbing, then monitor the system temporary directory for newly created .blend1 files. Note whether they appear during playback or only after it stops.
3. Repeat while rendering an animation (Render > Render Animation) and check the temp folder for Auto Save files appearing during the render or after completion.
4. Optionally launch Blender with --debug or open the scripting console to observe timer operator calls and compare timestamps with playback/render periods.

One Diagnostic Detail

What Blender version and render engine (Eevee, Cycles, Workbench) are you using? Some engines yield control differently between tiles or frames, which changes when the deferred Auto Save can execute.