How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix Construct 3 Local Storage Saves Lost Inside an itch.io Iframe

Q: What causes Construct 3 Local Storage saves lost inside an itch.io iframe?

Browsers partition or block storage for cross-origin iframes, so a game embedded on itch.io reads and writes a separate, often non-persistent, storage bucket.

Quick answer: Run the game on a domain where it is the top-level page, or enable itch's fullscreen/redirect so storage is first-party, and warn players that incognito blocks persistence.

When your game runs inside an itch.io iframe, the browser treats its storage as third-party and may wipe it between sessions. Serving it first-party restores persistence.

How to fix it

1. Avoid third-party storage

Modern browsers partition storage for cross-origin iframes. The Local Storage your game writes inside the itch frame may be isolated or cleared, losing saves.

2. Serve the game first-party

Use itch's option to launch the game in its own page/tab, or host the build on your own domain, so Local Storage is first-party and persists.

3. Offer an export/import fallback

Add a button that serializes the save to a string the player can copy or download, so progress survives even when browser storage is unreliable.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every Construct 3 error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.

Most of the time the fix is small. Seeing the failure clearly is the part that actually costs you.