JPG is commonly used for photographs and other images with many colors. A smaller file can be useful for a website or email, but the right result depends on the source, its dimensions, the chosen quality and where it will be displayed.
Before compressing a JPG
Keep the original file. Check its pixel dimensions, orientation, color profile if relevant, and whether it contains small text or sharp line art. If the image is much larger than its display area, resizing may be more useful than changing quality alone.
A repeatable browser workflow
- Open the JPG compressor and select a copy of the original.
- Choose a quality setting conservatively for the first pass.
- Download the result and compare it with the original at the size people will actually see.
- Inspect faces, text, edges, gradients and dark areas before publishing.
What can go wrong
Re-encoding an already compressed JPG can introduce additional artifacts. Strong compression may create block patterns, ringing near edges or loss of fine detail. A JPG is also not suitable when transparency is required. If the image is a logo, screenshot or diagram, compare PNG or WebP rather than assuming JPG is the best destination.
How to measure a useful result
Record the original and output bytes, dimensions, quality setting and format. The result should also be opened in the application or browser where it will be used. A smaller file is not automatically a better file if text becomes unreadable or the image no longer meets its purpose.
Privacy and limits
The tool page describes the processing path available in the current browser. Do not upload confidential material until you have confirmed that behavior and the applicable privacy policy. Keep the original until the downloaded file has been verified.
A practical comparison table
| Content | Inspect first | Possible alternative |
|---|---|---|
| Photograph | Texture and gradients | WebP or AVIF if supported |
| Screenshot | Small text and UI edges | PNG or a carefully tested WebP |
| Transparent graphic | Alpha channel | PNG, WebP or AVIF depending on delivery |
A failed test is useful information
If the downloaded JPG is not smaller or the visual result is unsuitable, check whether the source was already compressed, whether its dimensions were excessive, and whether a different format fits the content. Do not solve a compatibility problem by quietly lowering quality; document the trade-off and keep the original.
Publishing checklist
Before replacing the original web asset, check the output in the page template, at its actual display size and on a slower connection. Confirm that the filename, orientation, color appearance and download behavior are correct. If the image is part of a product, document or accessibility workflow, ask the person responsible for that workflow to approve the result.
Publishing checklist
Before replacing the original web asset, check the output in the page template, at its actual display size and on a slower connection. Confirm that the filename, orientation, color appearance and download behavior are correct. If the image is part of a product, document or accessibility workflow, ask the person responsible for that workflow to approve the result.
Sources and further reading
MDN’s image format guide describes where JPEG is appropriate and why sharp line art can behave differently from photographs. web.dev’s image performance guide recommends testing quality and file size together.