Numarly

Compress & Convert Image

Reduce file size or convert between JPEG, PNG, and WebP.

Click to select an image, or drag and drop it here

JPG, PNG, WebP, and other image formats

What is it?

This tool re-encodes an image to reduce its file size and/or convert it between JPEG, PNG, and WebP, entirely in your browser.

Formula Explanation

The image is drawn onto a canvas at its original resolution, then re-exported in the format and quality you choose. For JPEG and WebP, a lower quality setting compresses more aggressively (smaller file, more detail loss); PNG is always lossless, so its file size depends only on the image content, not a quality setting.

Example Calculation

A 2 MB PNG photo converted to JPEG at 80% quality might shrink to around 300-500 KB, since JPEG's lossy compression is far more efficient for photographic images than PNG's lossless compression.

How to Use

  1. Click the upload area or drag and drop an image onto it.
  2. Choose an output format: JPEG, WebP, or PNG.
  3. For JPEG or WebP, adjust the quality slider — lower means smaller file, more compression.
  4. Click Compress & Download to see the resulting size and save the file.

Benefits

  • Shrinks large photos for faster uploads and page loads without installing software.
  • Processes everything locally in your browser — images are never uploaded anywhere.
  • Shows the before/after file size so you can see exactly how much you saved.

Use Cases

  • Shrinking a phone photo before attaching it to an email with a size limit.
  • Converting a PNG screenshot to JPEG or WebP to save space on a website.
  • Reducing a batch of product photos to a consistent, smaller file size.

What Your Result Means

The percentage shown compares the new file's size to the original. JPEG and WebP at lower quality settings produce smaller files with more visible compression artifacts, especially in areas with fine detail or text; PNG never loses quality but often produces a larger file for photos.

Tips

  • WebP usually gives the best quality-to-size ratio for photos, if your use case supports it.
  • Start around 80% quality for JPEG/WebP — it's a good balance for most photos.
  • Use PNG for screenshots, logos, or images with sharp edges and text, where JPEG compression tends to look worse.

Common Mistakes

  • Converting a photo to PNG expecting a smaller file — PNG is often larger than JPEG/WebP for photographic images.
  • Setting quality too low, which introduces visible blocky artifacts, especially around text and edges.
  • Expecting quality to affect PNG output — PNG compression is always lossless.

FAQs

Are my images uploaded to a server?

No, all processing happens locally in your browser using the Canvas API — your images never leave your device.

Which format gives the smallest file size?

For photos, WebP or JPEG at a moderate quality setting is usually smallest. For flat-color graphics like logos or screenshots, PNG can sometimes be smaller too.

Why doesn't the quality slider affect PNG?

PNG uses lossless compression, so there's no quality trade-off to adjust — its file size depends only on the image content.

Does this resize the image too?

No, dimensions stay the same — use the Resize Image tool if you also want to change the pixel dimensions.

Images are read and re-encoded locally in your browser and are never uploaded to a server.

Last updated: August 1, 2026