Free Image Compressor – Resize & Convert Images Online
A free image compressor reduces the file size of JPEG, PNG and WebP images without visible quality loss. KnowAndAsk’s Free Image Compressor also resizes images and converts formats, all inside your browser, so your photos are never uploaded. No sign-up, no watermark.
- Input formatsJPG, PNG, WebP, GIF, BMP
- Output formatsJPEG, PNG, WebP
- PrivacyProcessed on your device
- PriceFree, unlimited images
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JPG, PNG, WebP, GIF or BMP
Choose imageSettings
Compare before & download
Drag the slider left or right to compare the original with your result.
Free image compressor: compress, resize and convert images online
How to compress, resize and convert an image
- Upload your JPEG, PNG, WebP, GIF or BMP image.
- Choose the output format and set the compression quality.
- Check the aspect ratio shown for your image, and choose a new ratio such as 1:1 or 16:9 if you need one.
- Enter a new width and height, or pick a percentage, to resize.
- Drag the comparison slider to check the result against the original.
- Click Download image.
Large images slow down websites, fill up inboxes and eat storage. This tool reduces file size while keeping the picture looking sharp, and lets you pick the right size and format for the job, whether it is a blog banner, a product photo, a social post or an email attachment.
Which image format should you choose?
| Format | Best for | Transparency | Compression |
|---|---|---|---|
| JPEG | Photos, gradients | No | Lossy, small files |
| PNG | Logos, screenshots, graphics | Yes | Lossless, larger files |
| WebP | Websites, almost everything | Yes | Lossy or lossless, smallest |
How to reduce image size without losing quality
A quality of 70 to 85 percent usually looks identical to the original on screen while cutting the file size dramatically. Resizing to the display size is often the biggest saving: a 4000 pixel wide photo shown at 800 pixels wastes most of its bytes. Use WebP for web pages, JPEG when you need the widest compatibility, and PNG only when you need sharp edges or transparency.
Why use a free image compressor?
Smaller images load faster, improve Core Web Vitals such as Largest Contentful Paint, save mobile data, and fit upload limits on email, job portals and government forms. Because this image compressor runs in your browser, nothing is sent to a server, which makes it a safe choice for personal photos and documents.
Recommended image sizes and quality
These are practical starting points. Always check the comparison slider before downloading.
| Use | Suggested width | Format | Quality |
|---|---|---|---|
| Blog or article image | 1200 px | WebP | 75 to 80% |
| Product photo | 1000 to 1600 px | WebP or JPEG | 80 to 85% |
| Email attachment | 1280 px | JPEG | 70 to 80% |
| Thumbnail | 300 to 400 px | WebP | 70% |
| Logo or screenshot | As needed | PNG | Lossless |
Image aspect ratio: common ratios and where to use them
The aspect ratio is the width divided by the height. This tool shows it for your original image and for the result. To change it, pick a ratio in the settings and choose whether to crop the edges or add padding.
| Aspect ratio | Typical use | Example size |
|---|---|---|
| 1:1 | Square social posts, profile photos, marketplace listings | 1080 × 1080 |
| 4:5 | Instagram portrait feed posts | 1080 × 1350 |
| 9:16 | Stories, Reels, Shorts, phone wallpapers | 1080 × 1920 |
| 16:9 | YouTube thumbnails, slides, website banners | 1280 × 720 |
| 3:2 | DSLR photos, prints, blog images | 1200 × 800 |
| 4:3 | Older monitors, tablets, compact cameras | 1024 × 768 |
| 1.91:1 | Facebook and Open Graph link previews | 1200 × 628 |
How to compress an image to 100 KB, 200 KB or 500 KB
First resize the image to the size it will actually be shown at. Then choose WebP or JPEG and lower the quality slider while watching the New file size. Stop when it reaches your target and the comparison slider still looks clean.
Common uses of an image compressor, resizer and converter
Faster page loads and better Core Web Vitals, smaller email attachments, meeting upload limits on forms and job portals, preparing thumbnails, and converting HEIC-style phone photos exported as PNG into compact JPEG or WebP files.
Frequently asked questions
What is the best free image compressor online?
A good free image compressor keeps quality high, works without uploading your files, and supports JPEG, PNG and WebP. KnowAndAsk’s Free Image Compressor does all three, adds resizing and format conversion, and shows a before and after slider so you can check quality before downloading.
How can I reduce image size to 100 KB or 200 KB?
Resize the image to the size it will be displayed at, choose WebP or JPEG, then lower the quality slider until the New file size shows your target. Quality between 60 and 80 percent usually reaches 100 to 200 KB for web photos without obvious loss.
Can I compress images on my phone?
Yes. The tool works in mobile browsers on Android and iPhone. Tap the upload area, choose a photo, adjust the settings and download the compressed image.
What is an aspect ratio and how do I find my image’s aspect ratio?
Aspect ratio is the proportion between an image’s width and height, written as width:height. A 1920 by 1080 image is 16:9. After you upload, this tool shows the aspect ratio of the original and of the new image next to their pixel sizes.
How do I resize or compress an image to a specific aspect ratio like 16:9 or 1:1?
Upload your image, open the Aspect ratio menu and choose a ratio such as 1:1, 4:5 or 16:9, or enter a custom one. Choose Crop to fill to trim the edges from the centre, or Fit with padding to keep the whole picture and add blank space. Then set the quality and download.
How do I compress an image online for free?
Upload your image, choose WebP or JPEG as the output format, adjust the quality slider, check the before and after comparison, then click Download. The tool is free and needs no sign-up.
Are my images uploaded to a server?
No. Compression, resizing and conversion happen locally in your browser, so your files never leave your device.
Does compressing an image reduce its quality?
JPEG and WebP use lossy compression, so lower quality settings remove some detail. At 70 to 85 percent the difference is usually hard to see. Use the comparison slider to check before downloading.
Which image format is best: JPEG, PNG or WebP?
WebP gives the smallest files for most web images and supports transparency. JPEG is best for photos when you need maximum compatibility. PNG is best for logos, screenshots and graphics that need sharp edges or transparency.
How do I resize an image without losing quality?
Enter the new width or height with Keep aspect ratio turned on, or use a percentage preset. Reducing dimensions keeps the picture sharp at its new size, and the quality slider controls the extra compression.
Why does the PNG quality slider do nothing?
PNG is lossless, so it has no quality setting. To shrink a PNG, reduce its dimensions or convert it to WebP or JPEG.
What happens to transparent backgrounds when converting to JPEG?
JPEG does not support transparency, so transparent areas are filled with white. Choose PNG or WebP to keep transparency.
Is there a file size limit?
There is no fixed limit, but very large images depend on your device memory and may process slowly.
Is the Free Image Compressor, Resizer & Converter really free?
Yes. It is completely free to use, with no watermark, no sign-up and no limit on the number of images.