What Is the Best Free Image Compressor Online?
Four options compared on batch size, file limits and whether your photo leaves your computer at all.
Short answer: for one photo, and especially a personal one, use a tool that compresses in your browser — MP3 Toolbox or Squoosh. For twenty images at once, TinyPNG is more convenient, at the cost of uploading them. For an exact file size such as 200KB, you need a tool built for a target rather than a quality slider.
What actually separates them
Every one of these produces a good result, because they all end up calling the same handful of encoders. The differences are structural: how many images at once, how large, whether the file is uploaded, and whether you can aim at a number instead of a percentage.
| MP3 Toolbox | In your browser, nothing uploaded · one image at a time · no account · can target an exact KB size |
|---|---|
| Squoosh | In your browser, nothing uploaded · one image at a time · side-by-side quality preview · no account |
| TinyPNG | Uploads to server, kept up to 48 hours · up to 20 images per batch, 5MB each · free conversion capped at 3 images |
| iLoveIMG | Uploads to server · batch supported · wide range of related tools · pushes sign-up for larger use |
Limits checked October 2026 against each service's own pages. Free tiers change — verify before relying on a number.
Which one to use
One photo, and it is personal — browser-based
A compressor that runs in your browser never transmits the image. That matters for a photo of your own face, a document, a child, or anything you would not hand to a stranger. Both MP3 Toolbox and Squoosh work this way, and you can prove it: load the page, disconnect from the internet, and compress anyway.
Squoosh, from Google, has the better interface for judging quality — a split view with the original on one side. Ours shows the real output size as you move the slider, because the image is genuinely re-encoded at each step rather than estimated.
A folder of twenty images — TinyPNG or iLoveIMG
Neither browser-based option does batches, and ours is explicitly one image at a time. If you are preparing thirty product photos, doing them individually is the wrong tool for the job and a batch service will save you half an hour.
The trade-offs are worth knowing: TinyPNG allows up to 20 images per batch at a maximum of 5MB each, caps free conversion at three images, and states that uploads are retained for up to 48 hours. That retention is perfectly ordinary for product photography and the wrong fit for anything private.
An exact file size — a target-based tool
This is where most compressors genuinely fail, and it is the single most common real-world requirement. A visa portal wants under 200KB. An exam registration wants under 100KB. A job application wants under 1MB.
A quality slider cannot hit those, because the relationship between quality and file size depends entirely on the picture. 70% might give you 180KB for one photo and 450KB for another, so you end up compressing, checking, adjusting, and checking again.
Compress to size takes the number instead: it encodes repeatedly, narrows in on the highest quality whose output still fits, and if even the lowest quality overshoots it reduces the dimensions and says so. In the browser, so the document never leaves your machine. There is a fuller write-up in compressing to an exact size.
A print or ID photo — a tool that handles all three constraints
An ID photo has three requirements at once: physical size in millimetres, resolution written into the file, and a file size cap. A compressor only addresses the third. Passport Photo Maker handles all three, and Set DPI rewrites just the resolution field without re-compressing the pixels at all. Background in the ID photo size guide.
The mistake that costs the most
People reach for a compressor when the real problem is dimensions. A photo straight from a phone is often 4000 pixels wide. Displayed in a web page at 800 pixels, three quarters of those pixels are thrown away by the browser on every single view.
Resize first, then compress. Halving the dimensions removes roughly three quarters of the data with no visible cost at the size it is actually shown — far more than any quality slider will give you, and without the artefacts. Resize then compress, in that order. The reasoning is in reducing image file size.
Two things worth knowing before you compress
Format matters more than the slider. Converting a screenshot or logo to JPEG usually makes it larger, not smaller, because JPEG is built for photographs and smears flat colour and text. Keep those as PNG, or use WebP, which does both jobs. See JPEG vs PNG vs WebP.
Compression usually strips metadata, but do not rely on it. Re-encoding through a canvas keeps only pixels, so camera, date and GPS are lost along the way. That is often welcome, but it is a side effect rather than a guarantee. If stripping metadata is the actual goal, use Remove EXIF and confirm with the EXIF viewer.
Quick decision list
- One personal photo — MP3 Toolbox or Squoosh, both in-browser
- Twenty product photos — TinyPNG or iLoveIMG
- Under 200KB for a form — Compress to size
- Photo is simply too big — resize first, then compress
- Screenshot or logo — keep it PNG, or convert to WebP
- Passport or ID photo — Passport Photo Maker
- Hundreds of images, repeatedly — a desktop tool or a script; a web page is the wrong place
Related guides
- Reducing image file size — why resizing beats compressing
- Compressing to an exact size — hitting 200KB, 100KB, 50KB
- JPEG vs PNG vs WebP — picking the format first
- Is it safe to convert files online — checking where processing happens
Summary
For a single image, a browser-based compressor is both the most private and the fastest option, and MP3 Toolbox and Squoosh both qualify. For batches, TinyPNG and iLoveIMG are more practical, at the cost of uploading. For an exact KB target, use a tool that accepts the number. And whatever you use, resize before you compress — it is where almost all of the saving actually comes from.