The Complete Image Conversion Guide: JPG, PNG, WebP, AVIF Explained
Why image conversion matters for your website
Image conversion is one of the most impactful things you can do to improve website performance. In fact, images typically account for 50–70% of a web page's total file size. Therefore, converting images to the right format — and compressing them properly — can dramatically reduce page load times.
According to Google's Web Performance guidelines, images are one of the top factors affecting Core Web Vitals scores. As a result, getting your image formats right directly impacts your SEO rankings.
Moreover, an image conversion guide like this one can help you understand which format saves the most file size without visible quality loss — so you can make the best decision for every use case.
Converting a 1MB JPEG image to WebP format typically reduces it to around 650KB at the same visual quality — a 35% reduction in file size with no visible difference.
The four main image formats explained
Before diving into when to convert images, it is important to understand the key differences between the four main formats used on the web today.
JPEG / JPG
JPEG (Joint Photographic Experts Group) has been the standard format for photographs since the 1990s. It uses lossy compression, which means some image data is permanently removed to achieve smaller file sizes. However, at quality settings of 80% or above, the quality loss is barely visible to the human eye.
- Best for: Photographs, product images, realistic images with many colours
- Not ideal for: Images with text, logos, or sharp edges
- Browser support: Universal — all browsers and devices
PNG
PNG (Portable Network Graphics) uses lossless compression, which means no image data is lost. Furthermore, PNG supports full transparency, making it the go-to format for logos, icons, and images that need to sit on coloured backgrounds.
- Best for: Logos, icons, screenshots, graphics with text, images needing transparency
- Not ideal for: Photographs — PNG files are much larger than JPEG for photos
- Browser support: Universal — all browsers and devices
WebP
WebP is a modern format developed by Google in 2010. It achieves 25–35% smaller file sizes than JPEG at equivalent quality, and it also supports transparency like PNG. Consequently, WebP is now the recommended format for most web images.
- Best for: Web images of all types — photos, graphics, and images with transparency
- Not ideal for: Situations requiring compatibility with very old browsers
- Browser support: All modern browsers (Chrome, Firefox, Safari, Edge) since 2020
AVIF
AVIF (AV1 Image File Format) is the newest image format and achieves even better compression than WebP — typically 40–50% smaller than JPEG at the same quality. However, browser support is still growing, so it is not yet universally supported.
- Best for: Maximum compression, cutting-edge web performance
- Not ideal for: Situations requiring broad compatibility with older browsers
- Browser support: Chrome 85+, Firefox 93+, Safari 16+
Image format comparison table
The following table summarises the key differences between all four formats to help you make the right image conversion choice:
| Format | Compression | Transparency | File size vs JPEG | Browser support |
|---|---|---|---|---|
| JPEG | Lossy | No | Baseline | Universal |
| PNG | Lossless | Yes | Larger | Universal |
| WebP | Both | Yes | 25–35% smaller | Modern browsers |
| AVIF | Both | Yes | 40–50% smaller | Newer browsers |
When to use each format — a practical image conversion guide
Now that you understand the formats, here is a practical image conversion guide for deciding which format to use in different situations:
Use JPEG when:
- You need maximum compatibility across all devices and browsers
- You are sharing photos via email or messaging apps
- The platform does not support WebP (some older systems)
Use PNG when:
- You need a transparent background (logos, icons, watermarks)
- You are working with screenshots or images that contain text
- You need lossless quality for editing purposes
Use WebP when:
- You are adding images to a website or web application
- You want the best balance of quality, file size, and browser support
- You need transparency but also want smaller files than PNG
Use AVIF when:
- You are optimising for Core Web Vitals and maximum page speed
- Your audience primarily uses modern browsers (Chrome, Firefox, Safari 16+)
- You want the absolute smallest possible file size
For new websites in 2024, use WebP as your default format. It gives you the best combination of file size reduction, quality, transparency support, and browser compatibility. Switch to AVIF only when your analytics confirm your users are predominantly on modern browsers.
How to convert images online for free
Converting images online is simple with our free image converter. In addition to format conversion, our tool also handles compression, resizing, and background colour replacement — all in one place, all in your browser.
Step 1: Upload your images
Go to our free image converter and drag and drop your images onto the upload area. You can upload multiple images at once for bulk conversion.
Step 2: Choose your output format
Select JPG, PNG, WebP, or AVIF as your output format. Furthermore, if you are converting PNG to JPG, you can also set a background colour to replace any transparent areas.
Step 3: Adjust quality settings
Use the quality slider to set your preferred quality level. For web images, 80–85% quality gives the best balance between file size and visual quality. In contrast, for archival or print use, set quality to 95%+ to preserve maximum detail.
Step 4: Download your converted images
Click Convert and download your images instantly. Because all processing happens in your browser, there is no waiting for uploads — conversion completes in seconds.
Try our free image converter
Convert JPG, PNG, WebP, AVIF — free, instant, no signup
Image conversion tips to speed up your website
Beyond simply choosing the right format, there are several additional image conversion best practices that can significantly improve your website's performance:
- Convert all JPEG images to WebP — this single step typically reduces your image payload by 30% with no visible quality loss.
- Resize images before uploading — there is no point serving a 4000×3000px image if it is displayed at 800×600px. Use our image resizer to resize to the exact display dimensions first.
- Compress images to 80–85% quality — most users cannot see the difference between 85% and 100% quality, but the file size difference is significant. Use our image compressor to reduce sizes further.
- Use lazy loading — add
loading="lazy"to image HTML tags so images below the fold are not loaded until the user scrolls to them. - Set explicit width and height attributes — this prevents Cumulative Layout Shift (CLS), which is one of Google's Core Web Vitals metrics.
- Use descriptive alt text — alt text helps search engines understand your images and improves accessibility for screen reader users.
Always keep your original high-resolution images backed up before converting. Once you convert from PNG to JPEG or reduce quality, the original data cannot be recovered from the converted file.
Frequently asked questions
Does converting JPEG to WebP reduce quality?
At quality settings of 80% or above, the quality difference between JPEG and WebP is negligible to the human eye. In fact, at equivalent visual quality, WebP files are significantly smaller than JPEG. Therefore, converting JPEG to WebP is almost always a net win — you get a smaller file with no perceptible quality loss.
Can I convert PNG to JPEG without losing transparency?
No — JPEG does not support transparency. Consequently, when you convert PNG to JPEG, transparent areas are filled with a background colour (usually white or black). However, you can convert PNG to WebP and keep the transparency, since WebP supports transparent backgrounds just like PNG.
Is AVIF better than WebP?
In terms of compression efficiency, AVIF is generally better than WebP — achieving 10–20% smaller files at equivalent quality. However, WebP has broader browser support. As a result, WebP is usually the safer choice for general web use in 2024, while AVIF is ideal for performance-critical applications where you can guarantee modern browser usage.
How many images can I convert at once?
Our free image converter supports bulk conversion — you can upload and convert as many images as you need in one go. Since all processing happens in your browser, there are no server-side limits.
Related articles in this series
This article is part of our complete image conversion guide series. Furthermore, each article below goes deeper into a specific topic: