Why image formats exist
An image format is simply an agreement about how to store the dots of a picture in a file. Different formats were invented to solve different problems. Some squeeze photographs into very small files by discarding detail the eye will not miss. Others keep every pixel exact so that text and logos stay crisp. Newer ones combine both approaches and add features such as transparency and animation.
Because no single format is best for everything, you regularly need to convert. A designer exports a PNG with transparency, a webmaster needs the lighter WebP version, a government form wants JPG. Understanding what each format does well lets you make the right choice instead of guessing.
JPG: the photograph standard
JPG, also written JPEG, has been the standard for photographs since the early nineties. It uses lossy compression: the picture is divided into small blocks and the fine detail that humans notice least is simplified. The file shrinks dramatically, often to a tenth of the raw size, and you control the trade-off with a quality setting.
Its strengths are universal support and small files for photos. Its weaknesses are that it cannot store transparency, it looks poor for sharp text and flat graphics because the block compression leaves fuzzy halos, and each re-save loses a little more quality. Choose JPG for photographs, especially when you are not sure where the file will end up.
PNG: sharp graphics and transparency
PNG uses lossless compression, which means the picture can be restored exactly. It supports full transparency, including soft edges, which makes it the favourite for logos, icons, screenshots and anything layered on top of other content.
The price is size. A photograph saved as PNG is often three to ten times larger than the same picture as a JPG, because natural images have lots of subtle variations that lossless methods cannot simplify. Use PNG when exactness matters more than size: interface screenshots, diagrams, text-heavy images and artwork with transparent backgrounds.
WebP: smaller files for the web
WebP was created by Google to make web pages lighter. It can work in lossy mode, like JPG, or lossless mode, like PNG, and it supports transparency and animation. In lossy mode it typically produces files twenty-five to thirty-five percent smaller than JPG at comparable visual quality.
All modern browsers display WebP. The remaining weakness is software outside the browser: some older editors, printers and upload forms still do not accept it. For a website you control, WebP is an excellent default. For files you send to other people, JPG remains the safer choice.
AVIF: the smallest, with conditions
AVIF is derived from a modern video codec and often yields the smallest files of all, sometimes half the size of a JPG with similar quality. It handles gradients and dark scenes well, supports transparency and wide colour, and is increasingly supported by browsers.
Two caveats apply. Encoding AVIF is slower and depends on your browser being able to create it, which is why the tool hides the option when your browser cannot. And not every device or program can open AVIF files yet. Use it for websites where you control the display and need maximum savings, not for files you email around.
A quick comparison
| Format | Compression | Transparency | Best for |
|---|---|---|---|
| JPG | Lossy | No | Photos, maximum compatibility |
| PNG | Lossless | Yes | Logos, screenshots, graphics |
| WebP | Lossy or lossless | Yes | Websites and apps |
| AVIF | Lossy or lossless | Yes | Smallest files for modern browsers |
If the table seems like a lot, remember this shortcut: photos go to JPG or WebP, graphics go to PNG, and AVIF is the optional extra when you need the very smallest file.
What happens when you convert
Converting does not magically improve a picture. It decodes the original into raw pixels and then encodes those pixels again in the new format. Going from a lossy format to another lossy format therefore adds a second round of compression loss. Going from JPG to PNG preserves everything the JPG still contains, but the PNG will be much larger and the old artefacts remain visible.
The best practice is to convert once, from the highest-quality original available, and to choose a high quality setting of 85 to 92 for lossy output. If you only have a JPG, do not expect conversion to bring back lost detail. Use conversion to make the file compatible or lighter, not to restore quality.
Transparent images and JPG
JPG has no transparency channel. When you convert a PNG, WebP or AVIF with transparent areas to JPG, those areas must be filled with something. Some converters fill them with black, which looks awful; others use white without telling you. In this tool you choose the fill colour, with white as the default, so logos and cut-outs end up on a clean background.
If you need to keep the transparency, convert to PNG or WebP instead. For a logo that must sit on different coloured backgrounds, never flatten it to JPG; keep a transparent PNG as your master.
Converting in bulk
Add many images at once and they are all converted to the format you select. This is perfect for preparing a folder of photos for a website, switching a shop catalogue to WebP, or turning a pile of screenshots into JPGs for an email. Download the whole set as a ZIP file to avoid saving each one individually.
File names are preserved with a short suffix so you can tell converted files from originals, and nothing is overwritten. Check a few results at full size before you convert a very large batch, particularly when you lower the quality for smaller files.
Choosing a format for specific situations
Uploading to a government or job portal. Use JPG, nearly always. These systems were built years ago and sometimes reject newer formats without a helpful message. If a PNG is refused, convert it to JPG at high quality and try again. Keep the dimensions modest and the size under the stated limit.
Building a website. Serve WebP to everyone, and consider AVIF for the largest hero images where savings are most visible. Keep a JPG fallback if you must support very old browsers. For logos and icons use SVG when possible, and PNG when you only have a raster file.
Sending pictures to friends. JPG is friendliest. Many people cannot open WebP or AVIF in their gallery apps, and a received file that will not open is worse than a slightly larger one.
Archiving originals. Do not convert your masters to lossy formats just to save space. Keep the camera’s original files, and create smaller copies for sharing. If you must archive screenshots or scans, PNG preserves them exactly.
Mistakes to avoid when converting
- Converting JPG to PNG to “improve quality”. It will not. The PNG simply stores the same flawed pixels in a bigger file.
- Saving a photo as PNG for the web. It makes pages slow for no visible benefit.
- Flattening transparency by accident. Check the result on a coloured background before using it in a design.
- Converting repeatedly. JPG to WebP to JPG to WebP gradually erodes quality. Always return to the original.
- Using extreme quality settings. Quality 100 produces huge files with almost no visible gain over 90.
- Ignoring metadata. Conversions may keep or drop camera and location data depending on the tool. If privacy matters, remove it deliberately with the EXIF tool.
How quality settings really work
When you convert to a lossy format, the quality slider decides how aggressively detail is simplified. Think of it as a dial between small and faithful. At 100 the encoder keeps almost everything, and the file becomes huge with no visible advantage. At 90 to 92 the picture looks identical to the original for nearly everyone, while the file is dramatically smaller. At 80 to 85 you save much more and only a trained eye on a large monitor can find the difference.
Below 70 problems start to appear: blocky patches in skies, smeared skin, ringing around text. These are the typical signs of over-compression. The right setting also depends on the content. A photo of a clear blue sky exposes banding quickly, while a busy street scene hides compression well because the eye is occupied with detail.
The best way to choose is to preview. Convert a representative image, compare the before and after at full size, and adjust by five points at a time. Once you find a setting that looks right, apply it to the whole batch, and you will avoid both bloated files and ugly artefacts.
Lossless formats ignore the slider entirely, so PNG output is always exact. If a PNG is too large, the fix is to reduce the number of colours or the pixel dimensions, or to switch to a lossy format when the image is a photograph.
Browser support and long-term safety
Formats come and go, so it helps to think about how long a file must stay usable. JPG and PNG are effectively permanent: every device made in the last twenty-five years can open them, and that will not change soon. WebP is now supported everywhere that matters on the web, and AVIF is following quickly, but neither is guaranteed to open in every desktop application or in older operating systems.
For important personal files such as family photos, scans of certificates and contracts, choose the most widely supported format and keep a copy. For web publishing, plan a fallback: serve a modern format to browsers that understand it and JPG or PNG to the rest. Many content systems do this automatically.
Finally, remember that conversion is not archiving. If a picture matters to you, store the original in at least two places, and treat converted versions as disposable working copies that you can always recreate from the master.
Frequently overlooked details
A few small points save big headaches. File extensions do not change a file’s true type: renaming a PNG to .jpg does not convert it, and many programs will refuse it. Colour profiles can shift colours slightly between formats and programs; for web use, standard sRGB is the safe target. Animated images such as GIFs lose their animation when converted to a still format, so only the first frame survives.
Very large images may need to be resized before conversion on phones, because memory is limited. And if a converted file looks slightly different on two devices, the cause is usually the screen’s calibration rather than the conversion itself.
Privacy and a final recommendation
Conversion happens in your browser, and your pictures are never uploaded. That matters for documents, IDs and personal photos, and it makes the process quick even on slow connections.
As a final rule of thumb: keep one high-quality master of every important picture, convert copies for each destination, and match the format to the job. JPG for photos shared widely, PNG for graphics and transparency, WebP for modern websites, AVIF when every kilobyte counts. Open the tool above to convert your images now.