A free image compressor shrinks the file size of a photo or graphic so pages load faster and uploads go through first time. Browser tools are quickest for a few images, while desktop apps and plugins handle whole folders or websites. Pick a format your platform supports, because the smallest file is no use if it won't display.
Big images are the most common reason a small business website feels slow. A photo straight from a phone can be many times larger than it needs to be, and visitors on mobile data feel every extra second.
Here are ten free image compressors in no particular order, sorted alphabetically, from simple web tools to apps for designers. Each description comes from the tool's own website, re-checked today. If speed is the bigger worry, my piece on why speeding up your website pays off is worth a read.
Compression comes in two types. Lossless keeps every pixel and shrinks the file a little, while lossy throws away detail you probably won't notice and shrinks it a lot. For most website photos, a gentle lossy setting is the sweet spot, and you won't see the difference.
Free image compressors compared
In the free plan column, Yes means the tool's own site describes a free version or free plan, Trial only means a time-limited trial, and No means neither is stated. Free versions often come with limits, so check what's included before you rely on one.
| Tool | Type | Good for | Free plan |
|---|---|---|---|
| Caesium | Desktop image compressor | Batches of photos offline | Yes |
| Compressor.io | Online image compressor | Quick single-image compression | Yes |
| iLoveIMG | Online image toolkit | Compressing and editing in one place | Yes |
| ImageOptim | Mac image optimiser | Lossless compression on Mac | Yes |
| Kraken.io | Image optimiser and API | Optimising images for developers | Yes |
| Optimizilla | Online image compressor | Choosing the quality level yourself | Yes |
| RIOT | Radical image optimisation tool | Side-by-side quality comparison | Yes |
| ShortPixel | Image optimisation service | Compressing images on a WordPress site | Yes |
| Squoosh | Browser image app | Testing modern formats like WebP | Yes |
| TinyPNG | Online compressor | Shrinking PNG and JPEG files | Yes |
Ten free image compressors to try
Caesium
Best for: People who want to compress folders of photos on their own computer without uploading them anywhere.
Compressor.io
Best for: Anyone who wants to drop in a JPEG, PNG, GIF or SVG and download a smaller version straight away.
iLoveIMG
Best for: People who want to compress, resize and convert images with a set of simple browser tools.
ImageOptim
Best for: Mac users who want to drag images onto an app and strip out extra data without losing quality.
Kraken.io
Best for: Developers and site owners who want a web interface now and an API for automating compression later.
Optimizilla
Best for: People who want to compare before and after previews and pick the quality level for each image.
RIOT
Best for: People who want to compare the original and compressed image side by side while adjusting settings.
ShortPixel
Best for: WordPress site owners who want images compressed automatically as they upload them.
Squoosh
Best for: Anyone who wants to try different formats and quality settings in the browser and see the result live.
TinyPNG
Best for: People who want quick, smart compression for PNG, JPEG and WebP images with drag and drop.
The image formats Google Search can read
Here's a detail worth checking before you convert everything. Google Search Central lists the image formats Google Search supports in the src attribute of an image tag: BMP, GIF, JPEG, PNG, WebP, SVG and AVIF. If you convert to anything outside that list, your images may not show up in image results.
WebP and AVIF often give the smallest files, but check that your website platform and email tools handle them too. A tiny file that won't display is worse than a slightly bigger one that does.
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What to check in a free image compressor
- Lossy or lossless: can you choose how much detail to keep?
- Formats: does it handle JPEG, PNG and WebP?
- Batch size: how many images can you do at once on the free plan?
- Privacy: are images uploaded, or processed on your own device?
- Metadata: does it strip location data from photos?
How to compress images for a website
- Resize the image to the largest width your site shows first.
- Run it through a compressor and compare it with the original.
- Pick the lowest quality where you can't see a difference.
- Name the file with real words, not a camera number.
- Upload and check the page on your phone.
Image mistakes that slow a site down
- Uploading full-size phone photos. Resize them first.
- Using PNG for photos. JPEG or WebP is usually far smaller.
- Compressing twice. Each pass of lossy compression loses more detail.
- Forgetting old images. Older posts often hide the biggest files.
A site audit shows which images are slowing you down, and my post on the benefits of a site auditor tool explains what to look for.
Do you make image optimisation tools? Tool makers can ask to be considered for a featured place on this list.
My plain advice on free image compressors
Resize first, compress second. Squashing a giant photo still leaves you with a giant photo, just a blurrier one. It's the order that matters, and it's the step people skip when they're in a hurry.
And make it a habit, not a project. If every image goes through a compressor before upload, you'll never have to fix a slow site later. That's a far nicer job than going back through hundreds of old posts, which is what most people end up doing when they don't.
Frequently asked questions
Does compressing an image reduce quality?
Lossless compression doesn't. Lossy compression removes some detail, usually without a visible difference at sensible settings.
What's the best format for website images?
WebP is a good default for most sites, with JPEG for photos and PNG for graphics that need transparency.
Can I compress images in bulk for free?
Yes. Several free tools handle batches, though some free plans limit the number per go.
Is it safe to compress images online?
For everyday images, yes. For private photos, a desktop app keeps files on your computer.
Why are my website images so big?
Phone cameras take very large photos. Resize and compress them before uploading.
Does compression remove location data?
Some tools strip metadata, including location. Check the settings if privacy matters.
Should I use AVIF?
It can give very small files, but check your website and email tools support it first.
What's the difference between compressing and resizing?
Resizing changes the pixel dimensions. Compressing reduces the file size.
Can WordPress compress images automatically?
Yes, with an image optimisation plugin that compresses files as you upload them.
How small should a website image be?
As small as possible without visible loss. Check how it looks at full width on a big screen.
