How to Convert Images Online (JPG, PNG, WebP and AVIF)

How to Convert Images Online (JPG, PNG, WebP and AVIF)

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Converting images between formats is something most people do only when something breaks. A website rejects a PNG. An email client will not open a WebP. A social platform compresses your JPG into a blurry mess. The need only becomes obvious when you hit a wall.

But converting formats is also an opportunity. A JPG converted to WebP might be half the size with the same quality. A PNG converted to JPG might drop from 2 MB to 200 KB. The right format for the right job saves bandwidth, speeds up websites, and avoids the headaches that come from using the wrong file type.

This guide explains how to convert images between JPG, PNG, WebP, and AVIF — when to use each format, what quality and file size to expect, and how to avoid the common mistakes that ruin images during conversion. If you want to convert something right now, use the ResizeLab image converter. It runs in your browser, so nothing uploads to a server.

Quick answer: how to convert an image online

  1. Open an image converter tool in your browser
  2. Upload the image you want to convert
  3. Select the output format (JPG, PNG, WebP, or AVIF)
  4. Adjust quality if the tool offers it
  5. Download the converted file

Quick takeaways

  • JPG — best for photos, smallest lossy files, no transparency
  • PNG — best for graphics, screenshots, logos, supports transparency
  • WebP — best for websites, smaller than both JPG and PNG, supports transparency
  • AVIF — best for maximum compression, modern browsers only
  • Convert first, then compress — get the right format, then shrink the file
  • Resize first, then convert — fewer pixels means smaller files after conversion

Supported image conversions

ResizeLab supports these conversions online in the browser:

All conversions run in the browser. Files are not uploaded to a server. Conversions work on desktop and mobile. No account or signup needed.

The four image formats explained

Before you convert anything, you need to understand what each format does and where it falls short. Each format makes different trade-offs between quality, file size, transparency, and compatibility.

JPG

JPG was created in 1992 for compressing photographs. It uses lossy compression, which means it discards some image data to make the file smaller. The human eye does not notice most of what gets removed, which is why JPG works so well for photos.

A JPG at 80% quality is typically 60–70% smaller than the uncompressed source. At 90% quality, the difference is almost invisible but the file is only 40–50% smaller. At 60% quality, the file is tiny but you will see compression artifacts. The sweet spot for most photos is 75–85%.

JPG does not support transparency. If you convert a PNG with a transparent background to JPG, the transparent areas become solid white. You cannot fix this after conversion. You need PNG or WebP for transparency.

JPG also struggles with sharp edges and text. A screenshot of a website saved as JPG will have fuzzy text. A logo with clean lines will look slightly blurred. The lossy algorithm treats all edges the same way, and fine details suffer.

JPG works everywhere. Every browser, every email client, every operating system, every social platform. It is the most compatible image format ever created. If you need a file that opens on any device without thinking about it, JPG is the safest choice.

PNG

PNG was created in 1996 to replace GIF. It uses lossless compression, which means every pixel is preserved exactly. You can open and re-save a PNG a hundred times and it never degrades. This makes PNG the right choice for any image where quality matters more than file size.

PNG supports transparency. You can have a fully transparent background, a partially transparent shadow, or a gradient fade. This is essential for logos, icons, overlays, and any image that needs to sit on top of a background without a solid box around it.

PNG is larger than JPG for photos. A photograph saved as PNG might be 3–5 times the size of the same image at 80% JPG quality. That is because PNG cannot discard detail the way JPG does. It compresses by finding patterns in the data, not by removing data. For photos, those patterns are not very efficient, so the file stays large.

PNG is perfect for screenshots, diagrams, text-heavy images, graphics with flat colors, and anything with sharp edges. The lossless compression preserves every pixel perfectly. Text stays readable. Lines stay crisp. Logos stay clean.

PNG is supported everywhere. Not quite as universally as JPG, but close. Every browser, every modern email client, every design tool. The only places PNG might cause issues are very old systems or specialized software that only accepts JPG.

WebP

WebP was created by Google in 2010 to replace both JPG and PNG on the web. It can do lossy compression for photos, lossless compression for graphics, and it supports transparency. In theory, it is the best of both worlds. In practice, it mostly lives up to that promise.

A WebP file at 80% quality is typically 25–35% smaller than a JPG at the same quality. A WebP lossless file is smaller than PNG. The transparency support is full alpha, just like PNG. For websites, WebP is the best all-around format.

WebP is supported by every major browser: Chrome, Firefox, Safari, Edge. The only exceptions are very old browsers and some enterprise software. For public websites, the coverage is effectively 100% of your visitors. For email, the support is weaker. Some email clients still do not display WebP images. For websites, use WebP. For email attachments, stick with JPG or PNG.

WebP is the default recommendation for any image that lives on a website. It compresses better than JPG, supports transparency like PNG, and is supported by every modern browser. If your CMS or CDN can serve WebP, you should use it for everything.

AVIF

AVIF is the newest format. It was finalized in 2019 and is based on the same video compression technology used for AV1 video. It compresses better than WebP. Much better. An AVIF file at the same visual quality is typically 20–50% smaller than the equivalent WebP.

The downside is compatibility. AVIF is supported by Chrome and Firefox, but Safari support is newer and less complete. Some older devices and browsers cannot display AVIF at all. If you serve AVIF, you need a JPG fallback for browsers that do not support it.

AVIF is also slower to encode. Converting a large photo to AVIF takes more processing time than WebP or JPG. For a single image, this is negligible. For a batch of a hundred images, it adds up. The JPG to AVIF converter handles this in the browser, but batch conversions will take longer than WebP.

AVIF is the best choice when you need the smallest possible file and your audience uses modern browsers. It is excellent for photo-heavy websites, galleries, and anywhere file size is the main concern. For general use, WebP is still the safer default. For cutting-edge compression, AVIF is the best option.

Format comparison

JPG vs PNG

JPG is smaller. PNG is higher quality. The choice depends on the content.

For photos, JPG wins. A 4000×3000 photo at 80% JPG quality is 1–2 MB. The same photo as PNG is 8–12 MB. The visual difference is invisible. The file size difference is massive. For photos, there is no reason to use PNG.

For graphics, PNG wins. A screenshot of a website saved as PNG is 500 KB and the text is perfectly readable. The same screenshot saved as JPG at 80% quality is 300 KB but the text is slightly fuzzy. The 200 KB savings are not worth the quality loss. For any image with text, sharp edges, or fine detail, PNG is the right choice.

For transparency, PNG is the only option between these two. JPG does not support transparency. If you need a transparent background, you must use PNG. If you want a smaller transparent file, convert PNG to WebP instead.

JPG vs WebP

WebP is almost always better than JPG for websites. A WebP at 80% quality is smaller than a JPG at 80% quality, with the same or better visual quality. The only reason to use JPG instead of WebP is compatibility. JPG works everywhere. WebP works on modern browsers but might fail on very old email clients or enterprise software.

For websites, use WebP. Serve JPG as a fallback for old browsers. For email attachments, use JPG. For social media, both work fine. Most platforms accept both and convert them automatically.

The JPG to WebP converter handles this conversion in the browser. Upload a JPG, get a smaller WebP file back. Nothing uploads to a server.

PNG vs WebP

WebP beats PNG for file size while keeping the same quality. A PNG with transparency is often 2–4 times larger than the equivalent WebP with transparency. The visual quality is identical. Both are lossless. The difference is compression efficiency.

For websites, WebP is the clear winner. Smaller files, same quality, same transparency. The only reason to keep PNG is for maximum compatibility. Some older systems, email clients, or design tools still prefer PNG. If you need to share a transparent image with someone using old software, PNG is safer. If you are putting the image on a website, use WebP.

The PNG to WebP converter is the fastest way to shrink transparent images without losing quality.

WebP vs AVIF

AVIF compresses better than WebP. For photos, AVIF is typically 20–50% smaller than WebP at the same visual quality. For graphics, the gap is smaller but AVIF still wins. The trade-off is compatibility and encoding speed.

WebP is supported by every major browser. AVIF is supported by Chrome and Firefox, with Safari support that is newer and less complete. If you serve AVIF, you need a JPG or WebP fallback. If you serve WebP, you might not need a fallback at all.

AVIF is also slower to encode. Converting a batch of photos to AVIF takes longer than WebP. For a single image, the difference is a few seconds. For a hundred images, it is minutes. For websites where you convert images as you upload them, the extra time is worth the file size savings. For quick one-off conversions, WebP is faster and almost as good.

If you want to test AVIF, the JPG to AVIF converter and PNG to AVIF converter let you compare file sizes directly.

When should you convert an image?

There are three main reasons to convert between formats: compatibility, file size, and quality control.

Compatibility is the most common reason. You have a WebP image and need to upload it to a platform that only accepts JPG. You have a PNG screenshot and need to attach it to an email that will not display PNG. You have an AVIF photo and need to share it with someone on an older device. Conversion solves the mismatch.

File size is the second reason. A PNG photo is 10 MB. A JPG of the same photo is 2 MB. A WebP is 1.5 MB. An AVIF is 1 MB. If you are uploading to a website, smaller files mean faster loading. If you are sending by email, smaller files mean they actually send. If you are storing thousands of images, smaller files mean less storage cost.

Quality control is the third reason. Social media platforms compress your uploads automatically. Instagram might compress your JPG more aggressively than you would like. By converting to the right format and quality before uploading, you control the result. A JPG at 80% quality uploaded to Instagram will look better than a raw 100% quality file that gets re-compressed by the platform to 60%.

Image conversion for websites and SEO

Website performance is one of the biggest reasons to care about image formats. Google measures page speed. Slow pages rank lower. Large images are the single biggest cause of slow pages.

Core Web Vitals, the three metrics Google uses to judge page speed, are directly affected by image size. The largest visible element on most pages is an image. If that image is 5 MB, the Largest Contentful Paint score will be poor. If it is 500 KB, the score will be good. The difference between those two is often just a format conversion and a compression pass.

The best workflow for websites is:

  1. Resize the image to the exact dimensions you need. A 6000×4000 photo does not need to be served at full resolution on a blog post. Resize it to 1200×800 first. The ResizeLab image resizer handles this.
  2. Convert to the right format. For photos, convert to WebP. For graphics with transparency, convert to WebP. For maximum compatibility, keep a JPG fallback. The ResizeLab image converter does this in one step.
  3. Compress to the right quality. WebP at 80% quality is the default sweet spot. JPG at 80% is the fallback. PNG at 100% for graphics where quality must be perfect. The ResizeLab image compressor handles this.

If your CMS supports responsive images, you can serve WebP to modern browsers and fall back to JPG for older ones. Most modern CMS platforms handle this automatically if you upload both formats. The key is to prepare the images correctly before uploading.

Image conversion for social media

Every social platform compresses images. Instagram, Facebook, LinkedIn, X — they all re-encode your uploads to save bandwidth. The problem is that their automatic compression is not always good. A photo that looks sharp on your screen might look soft after the platform processes it.

The best way to control quality is to convert and compress before uploading. A JPG at 80% quality is a good target for social media. The file is small enough to upload quickly, but the quality is high enough that the platform’s automatic compression does not make it worse. If you upload a raw uncompressed file, the platform might compress it more aggressively than you would like.

For profile pictures and logos, PNG is often better than JPG. The edges stay sharp. The text stays readable. The background stays transparent if the platform supports it. Convert PNG to WebP if the platform accepts it — the file will be smaller with the same quality.

For Instagram, the recommended size is 1080×1080 pixels. For LinkedIn, 1200×627 is the standard for link previews. For X, 1600×900 works well. Convert and resize to these dimensions before uploading. The platform will not resize for you, and an oversized image just gets compressed more aggressively.

Image conversion for email attachments

Email is the most restrictive environment for images. Most services limit attachments to 10–25 MB. Gmail is 25 MB. Outlook is 20 MB. A few uncompressed photos from a phone can exceed that easily.

Convert photos to JPG before attaching them. JPG at 80% quality drops a 5 MB photo to 1–1.5 MB. Five photos fit comfortably under any limit. The recipient sees the same image. The quality difference is invisible on a phone or laptop screen.

For graphics with text, PNG is better than JPG. The text stays readable. But PNG files are larger. If the graphic is complex, a PNG might be 2–3 MB. Consider converting to WebP if the recipient’s email client supports it. If not, compress the PNG as much as possible or use a lower-resolution version.

Never send AVIF or WebP in email unless you know the recipient can open them. Most email clients still do not support these formats. They will show as broken images or attachments that cannot be previewed. Stick with JPG for photos and PNG for graphics in email.

Conversion is rarely a standalone task. It is part of a larger workflow that includes resizing, compression, and cropping. Here is how the pieces fit together.

Convert then compress

Convert the image to the right format first, then compress it. A PNG converted to WebP and then compressed to 80% quality is smaller than a PNG compressed to 80% and then converted. The reason is that PNG compression is lossless. Compressing a PNG does not change the visual quality. Converting to WebP and then compressing gives you the format benefits and the quality benefits in the right order.

Use the ResizeLab image converter to convert, then the ResizeLab image compressor to compress. Or use the converter with quality settings to do both at once.

Resize then convert

Resize the image to the target dimensions first, then convert to the target format. A 6000×4000 image resized to 1200×800 and then converted to WebP is much smaller than a 6000×4000 image converted to WebP and then resized. Fewer pixels means less data to encode. The ResizeLab image resizer handles resizing and format conversion in one step.

Crop then convert

Crop the image to the exact area you need, then convert. Cropping removes unnecessary pixels before conversion, which makes the final file smaller. A photo cropped from 4000×3000 to 2000×1500 and then converted to WebP is half the size of the full image converted to WebP. The ResizeLab image cropper lets you crop visually with drag handles and then export in any format.

Convert images before uploading to websites

The most important workflow is pre-processing. Never upload raw camera files to a website. A 6000×4000 photo from a modern phone is 5–10 MB. Your website does not need that resolution. Your visitors do not need to download that much data. Your hosting bill does not need to serve that much bandwidth.

Resize to the display dimensions. Convert to WebP. Compress to 80% quality. Then upload. The result is a 200–400 KB file that looks identical to the original on screen. The page loads fast. The Core Web Vitals score is good. The visitors stay. The search rankings improve.

Common mistakes when converting images

Converting PNG to JPG for transparency

PNG supports transparency. JPG does not. If you convert a PNG with a transparent background to JPG, the transparent areas become solid white. You cannot restore transparency after conversion. If you need a smaller transparent file, convert PNG to WebP instead. WebP supports transparency and compresses much smaller than PNG.

Converting JPG to PNG expecting quality improvement

Converting a JPG to PNG does not improve quality. The JPG already lost data. Converting to PNG just preserves the degraded version losslessly. The file gets larger, not better. If you need a high-quality PNG, start from the original uncompressed source. Do not convert a JPG to PNG and expect miracles.

Ignoring quality settings

Some converters apply a default quality setting. For JPG and WebP, the default is usually 80–90% quality. This is fine for most cases. But if you are converting a logo or graphic with text, 80% quality might blur the edges. For text and graphics, use 95% quality or higher. For photos, 80% is the sweet spot. Always check the converted image before using it.

Converting the same file multiple times

Every JPG conversion loses data. If you convert a photo to JPG, then convert the result to WebP, then convert the WebP back to JPG, the quality degrades at each step. The final file is worse than converting once to the right format. Always keep your original uncompressed file as a master copy. Convert from the master, not from a previous conversion.

Using the wrong format for the job

Using PNG for a photo is a waste of space. Using JPG for a screenshot ruins the text. Using WebP for an email attachment might break the preview. Using AVIF without a fallback means some visitors see nothing. Match the format to the use case. Photos get JPG or WebP. Graphics get PNG or WebP. Email gets JPG or PNG. Websites get WebP with JPG fallback.

Frequently asked questions

Can I convert images without losing quality?

Converting between lossless formats does not lose quality. PNG to WebP in lossless mode preserves every pixel. Converting to a lossy format like JPG or WebP in lossy mode removes some data. At 80–90% quality, the visual difference is usually invisible. You cannot convert to JPG without losing some data, but you can convert without losing visible quality.

What is the best image format for websites?

WebP is the best all-around format for websites. It compresses better than JPG for photos, supports transparency like PNG, and is supported by every modern browser. For maximum compatibility, serve JPG as a fallback for older browsers. The JPG to WebP converter and PNG to WebP converter handle these conversions.

Is WebP better than JPG?

For websites, yes. WebP at 80% quality is typically 25–35% smaller than JPG at the same quality, with the same visual result. For email and older systems, JPG is still safer because the compatibility is universal. For modern websites, WebP is the better choice.

Should I use AVIF instead of WebP?

AVIF compresses better than WebP, but the compatibility is narrower. Use AVIF if your audience uses modern browsers and you need the smallest possible files. Use WebP if you want broad compatibility without fallbacks. Test the JPG to AVIF converter to compare file sizes for your specific images.

Can I convert images on my phone?

Yes. The ResizeLab image converter works on any modern mobile browser. Open the page, tap browse, select photos from your camera roll, choose the output format, and download the converted file. Works on Safari for iPhone and Chrome for Android.

Why are my converted images blurry?

Either the quality setting is too low, or you converted from a file that was already compressed. Every JPG conversion loses data. If you convert a JPG to WebP and then convert the WebP to JPG, the quality degrades twice. Always convert from the original uncompressed file. Keep the original as a master copy. Never convert a converted file.

Does converting images affect SEO?

Indirectly. The right format makes the file smaller. Smaller files load faster. Faster pages have better Core Web Vitals scores. Google uses Core Web Vitals as a ranking signal. The SEO benefit comes from the speed improvement, not the conversion itself. Converting a 5 MB PNG to a 500 KB WebP can improve your page speed by several seconds, which is a significant SEO win.

Conclusion

Image conversion is not just about changing file extensions. It is about matching the format to the job. JPG for photos. PNG for graphics. WebP for websites. AVIF for maximum compression. Each format makes different trade-offs between quality, size, transparency, and compatibility.

The best workflow is simple: resize to the right dimensions, convert to the right format, compress to the right quality, then upload. This keeps your files small, your pages fast, and your visitors happy. If you want to explore all the tools ResizeLab offers, visit the Online Image Tools Hub. You will find converters, compressors, resizers, croppers, and more — all running in your browser, nothing uploading to a server.