How We Compared These Tools
We tested each tool with a standard set of images: a 6MB portrait JPG from a modern smartphone, a 4MB landscape photo, a 1MB PNG screenshot with text, and a 2MB PNG graphic with transparency. We measured the output file size at the default settings, the visual quality at the output (looking for artefacts, blurring, and colour shifts), the upload/privacy model, and how many formats each tool supports.
This isn't a sponsored comparison. We're a free image compressor ourselves, so we have an obvious interest in this space, but we've tried to give each tool a fair hearing — including cases where competitors outperform us.
- TinyPNG / TinyJPG — The most popular web-based compressor
- Squoosh — Google's open-source browser-based tool
- Private Image Compressor — Our tool (browser-based, no uploads)
- Compressor.io — Cloud-based with multiple formats
- ImageOptim — Mac desktop app
- ShortPixel — Web tool and WordPress plugin
- Optimizilla — Simple web tool with visual quality preview
TinyPNG / TinyJPG
TinyPNG uses lossy compression for PNGs — specifically, it reduces the colour palette using a technique called quantisation, which produces much smaller files than standard lossless PNG compression while remaining visually near-identical for most images. For PNGs, it consistently outperforms browser-based tools that use the Canvas API.
✅ Pros
- Best-in-class PNG compression
- Simple drag-and-drop interface
- API available for developers
- Photoshop and WordPress plugins
- Batch upload (up to 20 at once)
❌ Cons
- Images uploaded to their servers
- 20 image/month free limit
- No AVIF on free tier
- No manual quality slider
- 5MB file limit on free tier
Best for: Developers, WordPress users, anyone who compresses lots of PNGs and doesn't have sensitive image content. Also the easiest tool for non-technical users who just want one-click compression.
Squoosh (by Google)
Squoosh is technically the most powerful free compressor available. It uses WebAssembly to run real codec encoders (MozJPEG, libavif, libwebp, OxiPNG) directly in your browser, giving you quality results that rival dedicated desktop software — all without uploading anything. The interface shows a side-by-side comparison of original vs. compressed.
✅ Pros
- No uploads — fully private
- Most formats of any free tool
- AVIF and JPEG XL support
- Side-by-side quality comparison
- Advanced codec settings
- Open source (Apache 2.0)
❌ Cons
- One image at a time only
- Learning curve for advanced settings
- Can be slow for AVIF encoding
- No batch processing
- Heavy page (requires good browser)
Best for: Developers, designers, and advanced users who want maximum control and format flexibility. Anyone who needs AVIF or JPEG XL output. Also excellent for privacy-sensitive images.
Private Image Compressor
Private Image Compressor focuses on being the simplest privacy-first option. It uses the browser's native Canvas API to compress images, which means no third-party codecs, no WebAssembly, and nothing leaving your device. The interface is stripped down: drag and drop, set a quality slider, see the live size and percentage saved, download. That's it.
✅ Pros
- Zero uploads — maximum privacy
- Simplest interface of any tool here
- Live stats (size and % savings)
- AVIF support in Chrome/Edge
- No account, no sign-up, no limits
- Works on large files (up to 50MB desktop)
❌ Cons
- PNG compression not as strong as TinyPNG
- One file at a time
- AVIF only works in Chrome/Edge
- No advanced codec settings
Best for: Anyone compressing sensitive images — medical photos, client work, personal images, business documents. Also ideal if you want the fastest, simplest experience without any learning curve. The GDPR implications of uploading images to third-party servers make browser-only tools the right choice for many professional contexts.
Compressor.io
✅ Pros
- Lossy and lossless modes
- SVG and GIF compression
- Clean, straightforward interface
- Good compression ratios
❌ Cons
- Only 1 free image per day (very restrictive)
- Uploads to cloud
- No AVIF
- Paid plan required for regular use
Best for: Occasional use when you specifically need SVG or GIF compression, which most browser-based tools don't support. The 1 image/day free limit makes it impractical for regular use without a paid plan.
ImageOptim (Mac)
✅ Pros
- Unlimited batch processing
- Multiple compression algorithms
- Strips EXIF metadata automatically
- Free with no limits
- Great for WordPress/web dev workflows
❌ Cons
- Mac only (no Windows/Linux)
- Desktop app to install
- No WebP or AVIF output
- Less intuitive for non-technical users
Best for: Mac users who need to compress many images at once — web developers, photographers, bloggers. Drag a whole folder onto ImageOptim and all images are compressed automatically. The best free batch compressor on Mac.
ShortPixel
✅ Pros
- Excellent compression algorithm
- AVIF and WebP output
- WordPress plugin (major draw)
- PDF compression
- CDN integration option
❌ Cons
- Only 50 free credits/month
- Cloud upload
- Best features require paid plan
- Account required for API/plugin
Best for: WordPress site owners who want automatic image optimisation on upload. Their WordPress plugin is one of the most popular in the ecosystem. For non-WordPress use, the 50 credit/month free tier is limiting.
Side-by-Side Comparison
| Tool | Privacy | Free limit | JPG quality | PNG quality | AVIF | Batch |
|---|---|---|---|---|---|---|
| TinyPNG | ⚠️ Uploads | 20/month | ⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ | Pro only | Yes (20) |
| Squoosh | ✅ Local | Unlimited | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ | ✅ Yes | No |
| Private Image Compressor | ✅ Local | Unlimited | ⭐⭐⭐⭐ | ⭐⭐⭐ | Chrome/Edge | No |
| Compressor.io | ⚠️ Uploads | 1/day | ⭐⭐⭐⭐ | ⭐⭐⭐⭐ | No | No |
| ImageOptim | ✅ Local | Unlimited | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ | No | ✅ Yes |
| ShortPixel | ⚠️ Uploads | 50/month | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ | ✅ Yes | Yes (50) |
Which Tool Should You Use?
The right tool depends on your specific situation. Here's a straightforward guide:
| Situation | Best tool | Why |
|---|---|---|
| Sensitive images (client work, personal, medical) | Private Image Compressor or Squoosh | Nothing uploaded — stays on your device |
| Maximum PNG compression quality | TinyPNG | Best-in-class PNG quantisation algorithm |
| Advanced format control (AVIF, JPEG XL) | Squoosh | Most formats, real codec encoders in browser |
| Mac batch processing | ImageOptim | Unlimited batch, multiple algorithms, free |
| WordPress automatic optimisation | ShortPixel | Best WordPress plugin, AVIF/WebP output |
| Simplest possible interface | Private Image Compressor | Drop file, set quality, download — nothing else |
| One-click compression, no thought required | TinyPNG | Default settings produce great results |
| Compressing SVG or GIF files | Compressor.io | Supports SVG and GIF (others mostly don't) |
Browser-based tools (including Private Image Compressor and Squoosh's OxiPNG mode) use standard PNG compression, which is lossless. TinyPNG uses a lossy quantisation approach that produces much smaller files by reducing the colour palette — often 50–70% smaller with near-identical visual quality. If PNG file size is critical and you don't have privacy concerns, TinyPNG wins for PNGs. For JPEGs and WebP, the difference between tools is much smaller.
When Is a Paid Tool Worth It?
For most personal users, free tools are entirely sufficient. The cases where paid tools genuinely earn their cost are:
- High-volume batch processing — If you regularly need to compress hundreds or thousands of images (e-commerce product catalogues, photography archive), TinyPNG's API or ShortPixel's bulk plans pay for themselves in saved time.
- WordPress automation — ShortPixel, Imagify, or EWWW Image Optimizer will automatically compress images as you upload to WordPress, handle thumbnails, and serve WebP/AVIF via CDN. Worth it for content-heavy WordPress sites.
- CDN + compression combined — Tools like Cloudinary or Imgix compress and serve images from a global CDN, transforming them on-the-fly. For high-traffic sites, the performance improvement justifies the cost.