Compress many images at once

How Batch Image Compressor works

The image is decoded into a canvas element, redrawn, and handed back as a new file. A canvas lives in the tab; closing it discards the pixels, which is why nothing needs deleting afterwards. Nothing is re-encoded on a server, so no copy of the original survives anywhere you cannot see.

That is the whole architecture: static files, one script, no upload endpoint to leak or log. Close the tab and the work is gone.

Why one file at a time is a business model

Almost every free compressor limits the queue rather than the maths: twenty files per drop, five per day, or a paid tier for “bulk”. The constraint is not technical. Compressing an image is a canvas resize plus one encode, and a browser does that in a few dozen milliseconds.

This tool takes the whole selection and loops. There is no queue on a server because there is no server: each file is decoded from a blob URL, drawn to a canvas at the capped width, and encoded with the browser's own JPEG or WebP encoder.

Hitting a size target, not just a quality number

A quality slider asks you to guess. A size target asks the question backwards: how low can quality go before the file fits? The tool binary-searches quality in six steps between 30% and 94%, and if even 30% is too large it shrinks the dimensions by 20% and tries again, up to four rounds.

That order matters. Reducing dimensions removes real detail but keeps the image clean; pushing quality far below 30% produces blocky artefacts at full resolution. For a 12-megapixel phone photo destined for a web form, capping the width at 1600 pixels costs nothing visible and saves more bytes than any quality setting.

What happens to EXIF, and why that is a feature

A photo straight from a phone carries EXIF: camera model, shutter count, the exact time, and often GPS coordinates accurate to a few metres. Canvas export writes fresh pixels and no metadata block, so all of it disappears.

For a listing, a CV attachment or anything posted publicly, that is the main privacy win of compressing in a browser. If you need the metadata kept — for archival or evidence — compress with a tool that copies it, because this one cannot.

JPEG, WebP, and why not PNG

PNG is lossless, so the only way to shrink it is to remove pixels, and a size target becomes a resolution target. JPEG and WebP both throw away information the eye is unlikely to miss, in exchange for files an order of magnitude smaller. At the same visual quality WebP is typically 25–35% smaller than JPEG, but a few desktop applications still refuse it, which is why JPEG is the default.

Everything comes back as one ZIP so the folder structure of a batch stays intact, and names stay unique when two files share a base name.

Good to know

• Works offline once loaded, including on flights and in locked-down networks.
• No file size limit beyond your device's own memory.
• Free to use, with no account and no usage counter.
• Results are produced locally, so they are not logged or shared with anyone.

Questions