Short answer: use JPEG for photos that must open everywhere, PNG for graphics, screenshots and anything that needs a transparent background or pixel-perfect edges, and WebP for images on a website, where it usually gives the smallest file for the same visual quality. If you’re unsure, keep your original file, then make a copy in the format your destination needs.

The rest of this guide explains why, shows what typically affects image file size, and gives step-by-step workflows for common jobs.

Why the format matters

An image format decides two things: how the picture is compressed, and which features the file can carry, such as transparency or animation. Choosing the wrong one usually doesn’t break anything. Instead, it quietly costs you. A photo saved as PNG can be ten times larger than it needs to be. A logo saved as JPEG loses its transparent background and gets blurry edges. A website full of oversized images loads slowly, especially on mobile data.

The good news is that only three formats cover almost every everyday need, and the rules for choosing between them are simple once you know what each one is designed for.

JPEG explained

JPEG (also written JPG; the two names mean the same format) has been the standard format for photographs for decades. It uses lossy compression: when you save, the encoder discards detail that the eye is unlikely to notice, which is why photos become dramatically smaller. The MDN image format guide describes JPEG as a lossy format, and the JPEG committee presents it the same way.

What that means in practice:

  • Photos look great at a fraction of the size. Smooth gradients, skin, skies and landscapes compress very well.
  • Every save loses a little more. If you open a JPEG, edit it and save it as JPEG again, the encoder discards detail again. Repeating this many times gradually adds blur and blocky artifacts, so keep an original and export copies from it.
  • No transparency. JPEG has no alpha channel. A transparent area must be filled with a solid colour, usually white, when you save.
  • Sharp edges suffer. Text, thin lines and flat colour areas can show faint “ringing” around edges, which is why screenshots and logos look worse as JPEG.

JPEG’s biggest strength is compatibility: practically every device, app, email client and website accepts it.

PNG explained

PNG uses lossless compression. The file gets smaller, but when it’s opened again every pixel is exactly as it was. The W3C PNG specification defines it as a lossless format and includes an alpha channel, which stores how transparent each pixel is.

That makes PNG the right choice for:

  • Logos and icons that must sit on different backgrounds.
  • Screenshots and interface images, where crisp text matters.
  • Diagrams, charts and illustrations with flat colours.
  • Working copies you plan to edit again, because saving doesn’t degrade them.

The trade-off is size. Lossless compression works brilliantly on flat colour, but a photo has millions of subtly different pixels, so a photographic PNG is often many times larger than a JPEG of the same picture.

WebP explained

WebP was created by Google for the web, and it can work in either mode: lossy, like JPEG, or lossless, like PNG. According to Google’s WebP documentation, WebP supports transparency in both modes and also supports animation. The format is now documented by the IETF as RFC 9649, with the media type image/webp.

Google reports that lossless WebP images are 26% smaller than PNGs, and lossy WebP images are 25–34% smaller than comparable JPEGs at equivalent quality. MDN gives a similar average for lossy WebP compared with JPEG. These are averages from the format’s authors, not a promise for every image, so it’s worth checking your own results.

Compatibility is no longer the obstacle it once was: MDN lists WebP support in Chrome, Edge, Firefox, Opera and Safari. Where WebP still trips people up is outside the browser: some older desktop software, printing services and upload forms only accept JPEG or PNG.

Real-world comparison

Comparison table of JPEG, PNG and WebP: compression type, transparency, animation and typical use

JPEG, PNG and WebP at a glance.

JPEG PNG WebP
Compression Lossy Lossless Lossy or lossless
Transparency No Yes Yes
Animation No Through the APNG variant Yes
Best for Photos Logos, screenshots, graphics Most images on websites
Main limitation Detail lost on every save Large files for photos Some older apps don’t accept it

Lossy vs lossless compression

These two terms explain almost every difference between the formats.

Lossless compression is like packing a suitcase neatly: everything that went in comes back out unchanged. It works by finding patterns, such as long runs of the same colour, and describing them efficiently. It’s ideal when exact pixels matter.

Lossy compression is closer to summarising a book. The encoder keeps what you’re most likely to notice and drops fine detail you probably won’t miss. A quality setting controls how much is dropped. High quality means bigger files and fewer artifacts; low quality means smaller files and visible damage.

A practical rule: use lossless for anything you’ll edit again or that contains text and sharp edges, and use lossy for final versions of photos that people will only view.

Transparency and compatibility

Transparency is often the deciding factor. If an image must sit on a coloured or patterned background, such as a logo on a website header, you need PNG or WebP. Converting a transparent PNG to JPEG always fills the transparent area with a solid colour.

Compatibility is the other side of the decision:

  • Sending to anyone, anywhere: JPEG for photos, PNG for graphics.
  • Publishing on your own website: WebP is usually the best default.
  • Uploading to a form or service: check which formats it accepts first.

Google’s guidance on images in search lists JPEG, PNG and WebP among the formats it supports, and recommends descriptive file names and good alt text. The format itself isn’t a ranking shortcut; a fast page and a clearly described image matter more.

Why file sizes vary: practical examples

File size depends on the picture as well as the format. A photo with fine detail and subtle colour changes may be far larger as a lossless PNG than as a JPEG. A flat-colour icon can compress efficiently as PNG, while a transparent logo may be a good fit for PNG or WebP. Neither case guarantees that one format will always produce the smallest file.

Example What to try What to check
High-resolution photo Resize to the dimensions needed, then export JPEG and WebP File size and visible details at the intended display size
Screenshot with text Save PNG, and compare with lossless WebP if supported Text sharpness and exact pixel reproduction
Logo with transparent background Compare PNG and WebP with transparency preserved File size and the appearance of edges on different backgrounds
Transparent logo exported to JPEG Check the flattened background JPEG cannot retain transparency, even if its file size is smaller

To reproduce a comparison yourself, start with one original image, make separate copies, keep the output pixel dimensions identical, and record each exported file’s byte count. Open each result at the same display size before deciding. Different encoders have different quality scales: setting both JPEG and WebP to 0.8 does not prove equal perceived image quality. If you change the pixel dimensions as well as the format, record those changes separately rather than attributing the entire difference to compression.

The comparison above is a decision guide, not a published benchmark. We have deliberately omitted exact test figures until the original test inputs, encoder settings, script and output log are available for independent re-checking.

When to resize, compress or convert

These three actions solve different problems, and the order matters.

Resize when the image is bigger than it will be shown

A 4000-pixel-wide phone photo displayed 800 pixels wide on a web page wastes most of its bytes. Reduce the pixel dimensions first with the ARAIJA Image Resizer, which keeps the aspect ratio locked so the picture doesn’t stretch.

Compress when the dimensions are right but the file is still heavy

Lowering the quality of a JPEG or WebP often removes a lot of bytes before any difference is visible. The ARAIJA Image Compressor shows the before and after size, and says honestly when a file can’t get smaller.

Convert when the format doesn’t fit the job

Use the ARAIJA Image Converter to switch between JPEG, PNG and WebP: for example, a WebP that an older app won’t open, or a PNG photo that should be a JPEG. It warns you before transparency is replaced with white in a JPEG.

All three tools run in your browser. The image isn’t uploaded to ARAIJA’s servers.

Common mistakes

  • Saving photos as PNG “for quality”. The file balloons with little visible benefit for viewing.
  • Saving logos and screenshots as JPEG. Edges blur and transparency disappears.
  • Re-editing the same JPEG repeatedly. Each lossy save adds damage. Edit from the original.
  • Compressing before resizing. Resize first, then fine-tune the quality.
  • Assuming WebP is always smaller. It usually is, but measure. The result depends on the image, encoder settings, and whether transparency must be preserved.
  • Forgetting the destination. A perfect WebP is useless if the form you’re uploading to only accepts JPEG.
  • Leaving file names like IMG_4821. Descriptive names and alt text help people, and Google recommends them.

Step-by-step workflows

Prepare a photo for a website

  1. Keep the original photo untouched.
  2. Resize a copy to the largest width it will actually appear at.
  3. Save it as WebP, or JPEG if your platform needs it, at a quality around 75–85.
  4. Compare it with the original at 100% zoom; lower the quality further if you can’t see a difference.
  5. Give it a descriptive file name and write alt text that explains what it shows.

Send photos by email or chat

  1. Resize very large photos, since most screens don’t need full camera resolution.
  2. Use JPEG for the widest compatibility.
  3. Keep the full-resolution original if the recipient may need to print it.

Prepare a logo or icon

  1. Start from the highest-quality version you have, ideally the designer’s original.
  2. Export PNG when you need maximum compatibility, or WebP for your own website.
  3. Check that the background is still transparent on both a light and a dark background.

Share a screenshot

  1. Use PNG so text stays sharp.
  2. Crop to the relevant area before sharing.
  3. If the file is still large and it’s for a website, try lossless WebP.

FAQ

Is JPG the same as JPEG?

Yes. JPG is simply a shorter file extension for the same format.

Does converting a JPEG to PNG improve its quality?

No. The detail lost when the JPEG was saved can’t come back. Converting only makes a lossless copy of what’s left, usually in a much bigger file.

Can every website and app open WebP?

Current versions of the major browsers can, according to MDN, but some older software and upload forms still can’t. Keep a JPEG or PNG copy for those.

What quality setting should I use?

There isn’t one right number. Around 75–85 is a common starting point for photos; check the result by eye and adjust.

Does a smaller image help search rankings?

Faster pages give a better experience, and Google’s image guidelines encourage good image practices, but no single format is a ranking trick.

Summary and next step

Choose by content and destination: JPEG for widely shared photos, PNG for graphics, screenshots and transparency, and WebP for images on your own website. Resize first, then compress, and convert only when the format doesn’t fit the job. Always keep your original.

Ready to try it? Resize a photo, compress it, and compare the before and after sizes in your browser.

Sources