Reduce an Image to Meet an Upload File-Size Limit

A file can be too large in bytes, too wide or tall in pixels, or in an unsupported format. These are separate checks. A 600 × 400 image can still exceed a small byte limit; a tiny WebP can still be rejected by a destination accepting only JPEG.

Write down the actual rules before changing the file. For the worked examples here, 500,000 bytes and 50,000 bytes are invented limits, not rules for any named website. Decimal 500 kB is 500,000 bytes, while 500 KiB is 512,000 bytes. When a label is ambiguous, consult the destination's own instructions.

Start from the original for every attempt. In Image Resize, width and height are exact inputs, so calculate a matching pair rather than changing just one arbitrarily. Our 1200 × 800 examples became 600 × 400: half the width and height, one quarter of the pixels, with the same 3:2 aspect ratio.

Download the resized copy. The original PNG inputs remained PNG at this stage. Reducing pixels changes available detail; do not do this if the destination needs the original dimensions or the text becomes unreadable.

This owned 600 × 400 test image contains a circle and a square. We downloaded two PNG outputs from Image Resize on September 8, 2026, starting from the same original each time. At 300 × 200, both dimensions are multiplied by 0.5. At 300 × 300, width is multiplied by 0.5 but height by 0.75: the circle becomes a tall oval and the square becomes a tall rectangle.

The figures below use the same display width so you can compare shapes; labels give the actual file dimensions. The original and proportional copy should have the same proportions. The square output retains all the content but distorts it. These are actual browser outputs, not a simulation of cropping.

To preserve proportions, new height = original height × new width ÷ original width. For 600 × 400 at a width of 300, height = 400 × 300 ÷ 600 = 200. If you start from a required height, use new width = original width × new height ÷ original height. For non-integer results, round to a whole pixel and check whether that small ratio difference is acceptable.

Image Resize applies both entered dimensions exactly. Its presets choose dimensions; they do not lock the source aspect ratio. It does not crop or add padding. If an upload requires exactly 300 × 300 while your source is 3:2, choose a separate crop or padding workflow that the destination accepts instead of forcing a square resize.

The synthetic texture began at 2,884,537 bytes. Direct WebP at 80% and unchanged 1200 × 800 dimensions produced 658,298 bytes, still above the invented 500,000-byte limit. Compression alone at this setting did not solve the task.

Resizing the original to 600 × 400 produced a 798,212-byte PNG. Processing that resized PNG as WebP at 80% produced 118,880 bytes, which fits the example byte limit. This is a synthetic pixel-noise case; it does not prove acceptable photographic quality or compliance with a real destination.

The text fixture began at 110,711 bytes. At full dimensions, WebP at 80% produced 65,234 bytes, still above an invented 50,000-byte limit. Resizing to 600 × 400 produced a 65,924-byte PNG; converting that file to WebP at 80% produced 27,788 bytes.

We opened the final text output and could read the sample labels at their native display size. That observation applies to this fixture. Small print, different fonts, scanned pages or another viewing size may require more pixels. A successful byte check does not establish accessibility or readability for every reader.

If the file remains too large, compare another supported format or a lower lossy quality setting, checking the result each time. If it fits but looks poor, return to the original and try a different combination instead of compressing an already damaged output again.

If the bytes fit but the site still rejects the upload, recheck the extension, actual encoding, dimensions and destination-specific rules. Do not rename a file to imitate another format. If the requirements conflict with legibility, ask for an accepted alternative rather than discarding essential information.

Open the downloaded file, confirm its pixel dimensions and byte size, and inspect fine details and the background. Keep the original until the receiving site has accepted and displayed the file correctly.

These tools create local copies; they do not control another site's upload process or guarantee metadata removal. For a general preparation checklist, use Image Size and Aspect Ratio Checklist. For choosing a format, use the linked JPEG/PNG/WebP comparison.