What causes a web game canvas not resizing?

The canvas backing-store size is fixed and not updated on window resize, or CSS size and backing size are confused, so the game does not fill the window or appears stretched.

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 a Web Game Canvas Not Resizing with the Window

Quick answer: Listen for the resize event and update both the canvas backing size (width/height attributes) and the renderer viewport, keeping CSS size in sync, accounting for device pixel ratio.

A canvas that does not resize ignores the window resize event or confuses CSS and backing size. Handling resize fixes it. Here is how.

How to fix it

1. Handle the resize event

Listen for window resize and update the canvas. Without handling it, the canvas keeps its initial size while the window changes, so the game does not fill or fit the new dimensions.

2. Update backing size and viewport

Set the canvas width and height attributes (the backing store) to the new size times the device pixel ratio, and update the renderer's viewport. CSS size alone only stretches the existing pixels.

3. Debounce and preserve aspect

Resize can fire rapidly; debounce the handler so you do not thrash. Decide whether to fill or letterbox, and apply a consistent aspect handling so the game looks right at any window size.

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 HTML5 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.

The errors you never hear about are the ones quietly costing you players. Visibility turns them into a worklist.