What happens when an image is compressed locally in the browser.
Quick answer
The browser canvas re-encodes the image; JPEG quality is lossy and lower values generally reduce file size.
Canvas
The browser canvas re-encodes the image; JPEG quality is lossy and lower values generally reduce file size. In this context, canvas matters because the output should match the task rather than simply produce a file or string. Review the result against the original input and keep an untouched copy when the workflow changes a file.
Privacy
The browser canvas re-encodes the image; JPEG quality is lossy and lower values generally reduce file size. In this context, privacy matters because the output should match the task rather than simply produce a file or string. Review the result against the original input and keep an untouched copy when the workflow changes a file.
Metadata
The browser canvas re-encodes the image; JPEG quality is lossy and lower values generally reduce file size. In this context, metadata matters because the output should match the task rather than simply produce a file or string. Review the result against the original input and keep an untouched copy when the workflow changes a file.
Practical example
Use the matching Get Tools Lab Image Compressor tool with a small, non-sensitive example first. Confirm the expected result before using a larger or important input.
Privacy and limitations
Processing behavior depends on the tool. Priority browser-local tools identify that behavior on the tool page. A local browser workflow reduces server upload exposure, but it does not remove the need to protect the source file, device and downloaded result.
Related workflow
Open Image Compressor. You can also use the related comparison, glossary and topic pages to understand the format and trade-offs.