Compress Images Online for Free
Choose images and settings
Accurate before-and-after preview
Original
Compressed
- Original size
- Output size
- Bytes saved
- Reduction
- Dimensions
- Format
- Quality
The checkerboard reveals transparent areas. Use zoom to inspect compression detail.
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Processing queue and downloads
How to compress an image
- Choose one image or a batch, then select JPG, PNG, WebP, or supported AVIF output.
- Use a quality preset, enter a maximum KB/MB target, and optionally limit dimensions.
- Select Compress images, compare the actual output, then download one file or a local ZIP.
Measured savings
Every result uses the generated Blob, not an estimate. The formula is reduction = (original size − compressed size) ÷ original size × 100. For example, reducing a 2,000 KB photo to 500 KB saves 1,500 KB, a 75% reduction.
Quality and file size are not linearly related: quality 50 does not mean half the bytes. Image detail, noise, dimensions, transparency, encoder, and format all affect the result, so no universal quality-to-KB formula exists.
Choose the right image format
| Format | Best for | Transparency | Compression | Typical quality | Compatibility |
|---|---|---|---|---|---|
| JPG | Photos, email, application portals | No | Lossy | 70–90 | Universal |
| PNG | Logos, screenshots, diagrams, text | Yes | Lossless or reduced palette | Not applicable to lossless PNG | Universal |
| WebP | Web images, social posts, photos and graphics | Yes | Lossy in this tool | 70–88 | Current major browsers |
| AVIF | Modern websites and high-resolution photos | Browser-dependent | Lossy in this tool | 55–80 | Current encoders vary; option is disabled if unavailable |
Practical starting points
- Website hero: WebP around quality 80 and maximum width 1920 px.
- Email attachment: choose a 1 MB target and let the tool reduce dimensions if required.
- Social post: WebP or JPG, maximum width 1280 px.
- Application or passport portal: use its exact 50 KB, 100 KB, or 200 KB maximum and the required format.
- High-resolution phone photo: resize to 1920 px before lowering quality aggressively.
Image compressor FAQs
How do I compress an image online without uploading it?
Choose or drop one or more images, select the output settings, and press Compress images. Encoding and ZIP creation happen in your browser; files are not uploaded or stored.
Will compression reduce image quality?
Lossy JPG, WebP, and AVIF output can remove detail, especially at low quality settings. Use the before-and-after preview and start with Balanced. Lossless PNG preserves pixel data, while reduced-palette PNG can change colours.
Can I reduce image size to under 200 KB or 1 MB?
Yes. Select Target file size, enter a value or choose a preset, and the tool searches for the highest quality below that maximum. If quality alone is insufficient, it progressively reduces dimensions without upscaling.
Is this image compressor private?
Yes. Processing and ZIP creation happen locally in your browser. Images are not transmitted to or stored by Starlight Tools, and no account or watermark is used.
Does the compressor preserve transparency?
PNG and WebP preserve transparent areas when the browser encoder supports them. JPG has no transparency, so transparent pixels are placed on a white background.
What happens to EXIF, GPS, colour-profile, and copyright metadata?
Canvas export removes EXIF, GPS, orientation, colour-profile, and copyright metadata by default. The optional preserve setting copies supported JPEG or PNG metadata where possible and resets JPEG orientation after pixels are normalised; preservation is not available for WebP or AVIF output.
Which input and output formats are supported?
JPG, PNG, and WebP inputs work in current major browsers. AVIF and HEIC input depend on the browser's decoder. Outputs are JPG, PNG, WebP, and AVIF when the browser encoder supports them. Animated GIF, PNG, and WebP files are rejected rather than silently flattened.
Are there file or image limits?
There is no server upload limit, but browser memory is finite. The tool warns above 25 megapixels or 30 MB and rejects images above 80 megapixels to reduce mobile crashes. Large batches are processed one image at a time.
Does it work on mobile devices?
Yes, in current mobile browsers with canvas and Blob support. Asynchronous encoding, one-at-a-time batch processing, cancellation, and dimension safeguards help limit interface freezes and memory use.
Why might a PNG not become smaller?
PNG is lossless, so a source that is already optimised may not shrink when re-encoded. The tool keeps an unchanged PNG when that is smaller, while reduced-palette mode can save more by limiting colours. Resizing or choosing WebP may produce a smaller file when appropriate.
Tested for the standard Canvas, Blob, object URL, and file APIs used by current Chrome, Edge, Firefox, and Safari. HEIC/AVIF decoding and AVIF encoding remain browser-dependent.