Batch Image Compressor

Batch Image Compressor — runs in your browser

Everything below happens on this page. No file is uploaded, there is no account, and nothing is watermarked.

This compressor runs entirely on your own device. When you drop files in, your browser decodes each one, re-encodes it to a lower byte count, and hands you the result — the file bytes never travel over the network, and there is no server holding a copy at any point.

You can drop a whole folder at once, set one quality level for everything, and download the results as a single zip. That makes it practical for cleaning up a shoot before uploading to a client, or for cutting a batch of generated images down before they go into a video editor.

What it does

Everything is done on your device, so there is nothing to upload and nothing to wait for a queue.

How to use it

Four steps, and none of them leaves your machine.

1. Drop the files in

   Drag images or a whole folder onto the page. Nothing leaves the browser.

2. Set quality and format

   Pick JPEG, WebP or PNG. WebP usually wins on photographs; PNG only helps for flat graphics.

3. Run the batch

   Each file is re-encoded in turn and the before/after byte count is shown per file.

4. Download the zip

   One archive with every compressed file, named to match the original.

What people use it for

The jobs this actually gets used for.

Why compress on your own machine

The compression maths is the easy part. Where the files go is the actual question.

Any browser can re-encode a JPEG or PNG — Canvas does it natively. The reason online compressors exist as separate services is billing and convenience, not capability. That means when you use one, your images pass through infrastructure you do not control, are often retained for hours or days, and may be used to train something.

Running locally removes that question entirely. The file is read from your disk into a memory buffer, decoded, re-encoded, and written back out. There is no network request carrying image data, so there is nothing to leak, nothing to be subpoenaed, and nothing to delete later.

The honest trade-off is speed. A batch of 200 files will visibly pause the interface on a lower-end laptop, because the work competes with the page for the same CPU. A native desktop tool does it faster. In exchange you keep the originals exactly where they are and gain the ability to do this on a machine with no network access at all.

What it cannot do

The honest list, so you do not find out halfway through a batch.

• Lossy only. There is no lossless PNG recompression here, so a flat graphic may not shrink much and re-encoding it repeatedly will degrade it.
• Animated GIFs are not processed frame by frame — they are treated as a single still and will lose their animation.
• Very large images (over about 8000px on a side) can exhaust memory in the tab before finishing.

Built on open source

The processing is done by a published, licensed library — you can read exactly what runs on your device.

This page uses compressorjs (5.7k), released under MIT. It runs entirely in the browser tab, which is why your files never leave the machine: there is no server to send them to. Nothing here calls an API, and there is no account to create.

Related guides

Longer reads on the same workflow, from the OpenFilmo blog.

Other free browser tools

Same principle: they run on your device and cost nothing to use.

Frequently asked questions