Resizing a very large image fails or freezes on my phone. Why?
Because the tool draws the picture on a canvas in memory, a big canvas needs a lot of it, and phones give the browser far less memory than desktop computers. So a size inside the tool's limits can still fail on a phone in particular. The fix: choose a smaller output, close other tabs, or do the large resize on a computer.
How much memory an image really needs
The image file on your device is compressed, but inside a canvas every pixel takes four bytes: red, green, blue and transparency. So a picture whose file is a few megabytes can need many times that in memory.
An 8000 × 6000 output is accepted by the tool, being 48 megapixels, under the 50 limit.
A canvas that size alone needs about 192 MB of memory.
At the same time the tool keeps a canvas of the original picture, plus intermediate canvases while scaling down.
A 3000 × 2250 output from the same photo needs a canvas of only about 27 MB.
On a computer these figures usually pass without trouble; an 8000 × 6000 JPEG output was tested in desktop Chromium. On a phone with limited memory and other apps and tabs open, the browser may refuse to create the canvas or close the page to protect the system.
What failure looks like
- An error message where the result should be, instead of the preview.
- The processing indicator staying on for a long time with no result.
- The page suddenly reloading, or the browser itself closing.
What to do
- Ask first: do you need that size? Most online uses are fine with under 3000 px on a side. Type a smaller width with the ratio lock on.
- Close other tabs and apps before trying, to free memory for the browser.
- If you really need the large size, such as a print file, open the Image resizer on a computer.
- Avoid rapidly changing the numbers while it works, since every change starts a new round of processing.
And the input picture?
The picture you choose has a limit as well: files up to 40 MB and up to 50 megapixels. Photos from some very high-resolution phones exceed it, and the tool rejects them with a clear message. Even pictures within the limit can strain an older phone, because decoding alone needs a canvas at their full size. If all you want is a lighter file at the same dimensions, try the Image compressor on a computer for the whole set.
Common questions
Is it the tool or my phone?
The tool runs inside your browser and relies on its memory. The same size may work on a recent phone and fail on an older one.
Would another format help?
The format changes the size of the output file, but the memory needed while drawing depends on the pixel count, so reducing the dimensions is what makes the difference.