JPEG vs PNG vs WebP: Which Image Format Should You Use?

Choosing the wrong image format is one of the most common and costly mistakes in web development. A photograph saved as a PNG is typically 5–10× larger than the same image saved as a JPEG. A JPEG saved where a PNG was needed will have no transparency and ugly compression artefacts around text. And ignoring WebP entirely means missing out on 25–35% smaller files with better quality.

This guide breaks down the three most important web image formats — JPEG, PNG, and WebP — across every dimension that matters: compression efficiency, quality, transparency support, animation support, browser compatibility, and ideal use cases.

JPEG (Joint Photographic Experts Group)

JPEG was standardised in 1992 and remains the dominant format for photographic images on the web. It uses lossy compression — meaning it permanently discards some image data to achieve small file sizes. It does this exceptionally well for photographs because the data it discards (subtle colour variations, fine high-frequency detail) is almost invisible to the human eye.

At quality level 75–80%, a JPEG photograph is visually indistinguishable from the original to most people, yet it is typically 10–20× smaller than the uncompressed raw data. This makes JPEG the best choice for:

• Photographs (people, landscapes, products, food)
• Any image with many colour gradients or complex textures
• Hero images and large page backgrounds
• Any situation where you need small file sizes and transparency is not needed

JPEG's weaknesses are well-known: it does not support transparency (alpha channel), each save introduces additional quality loss (never re-save a JPEG as a JPEG if you can avoid it), and it handles flat-colour graphics and text poorly — the compression algorithm creates blocky artefacts around sharp colour boundaries.

PNG (Portable Network Graphics)

PNG was created in 1996 specifically as an open-source, patent-free alternative to GIF with better support for full-colour images. It uses lossless compression — every pixel is stored exactly. The result is that PNG files are much larger than JPEGs for photographic content but preserve every detail perfectly.

PNG's defining feature is its alpha channel — each pixel can store a transparency value from 0 (fully transparent) to 255 (fully opaque). This makes PNG the only practical choice for:

• Logos with transparent backgrounds
• Icons and UI elements that need to overlay other content
• Screenshots (especially those containing text, which JPEG compresses poorly)
• Graphics with flat colours and sharp edges

For photographs, however, PNG is the wrong choice. A photograph that compresses to 80 KB as a JPEG might be 800 KB–2 MB as a PNG. There is no quality advantage for photographs — you are just paying a massive file-size penalty for no benefit.

There are two main variants: PNG-8 (256 colours, like GIF) and PNG-24 (16 million colours + full alpha). For web use, PNG-24 is standard unless you specifically need to support very old browsers or need extremely small icon files.

WebP

WebP was developed by Google and publicly released in 2010. It is a modern format designed specifically to replace both JPEG and PNG on the web, offering:

• 25–35% smaller than JPEG at equivalent visual quality (lossy mode)
• 26% smaller than PNG for lossless images (lossless mode)
• Full alpha channel transparency (even in lossy mode)
• Animation support (as a replacement for GIF)

WebP achieves this through a more modern compression algorithm that JPEG was designed without accounting for. It divides images into segments and uses a combination of prediction coding, arithmetic entropy coding, and more efficient block transforms.

Browser support for WebP is now excellent: Chrome, Firefox, Safari (since 2020), Edge, and Opera all support it — covering over 97% of global web traffic. Internet Explorer does not support WebP, but its market share is negligible and declining.

The main consideration before switching entirely to WebP is workflow: some older software tools (Photoshop versions before 2021, some mobile gallery apps) cannot open WebP files without a plugin. If your images need to be downloaded and edited by users, JPEG or PNG may be more practical.

Format Comparison at a Glance

When to Use Each Format

Use JPEG when:

• You are displaying a photograph or realistic image
• File size is critical and transparency is not needed
• The image will be displayed in an email (WebP lacks universal email client support)
• You are preparing images for systems that may not accept WebP

Use PNG when:

• You need a transparent background (logo on a coloured page, watermark, overlay)
• The image contains text, charts, or sharp edges where JPEG artefacts would be visible
• You are saving a screenshot for documentation or tutorials
• Pixel-perfect accuracy is required (medical imaging, technical diagrams)

Use WebP when:

• You can serve WebP to modern browsers while providing JPEG fallback via the HTML <picture> element
• Bandwidth savings are a priority (high-traffic e-commerce, news sites, mobile apps)
• You need transparent background with lossy compression (WebP supports this; JPEG does not at all)
• You are replacing animated GIFs (WebP animation is far more efficient)

Implementing WebP with JPEG Fallback

The safest way to use WebP today is with the HTML <picture> element, which lets browsers choose the best format they support:

This pattern ensures modern browsers receive the smaller WebP file while Internet Explorer and older Safari versions fall back to JPEG. It requires generating both file versions but delivers the best performance and compatibility trade-off.

What About AVIF?

AVIF is the newest major image format, based on the AV1 video codec. It offers 40–50% smaller files than JPEG at equivalent quality — even better than WebP. Browser support reached Chrome, Firefox, and Safari by 2023, covering around 89% of users as of 2026.

AVIF is worth considering for new projects, but encoding is significantly slower than JPEG or WebP, making it less practical for real-time browser-based compression. For existing workflows, WebP remains the best performance-vs-compatibility choice.

Conclusion

The format decision is not complicated once you internalise the basic rules: JPEG for photos where file size matters and transparency is not needed; PNG for graphics, logos, and anything requiring transparency or pixel accuracy; WebP when you want the best of both worlds and can manage browser compatibility. Getting this decision right consistently is one of the highest-value things you can do for your website's performance.