You have a PNG but the platform needs a JPG. Or a WebP that does not open in an older program. Or a photo you want to convert to WebP for better web performance. Image format conversion is one of those small tasks that comes up constantly, and most people either install software to handle it or struggle with whatever their operating system provides by default.
Understanding which format to use when, and how to convert quickly, saves time and avoids quality issues.
The main image formats and when to use each one
JPG is the standard for photographs. It uses lossy compression, meaning it discards some image data to reduce file size. The quality loss is usually invisible at settings above 80 percent. JPG does not support transparency. Use it for photos, product images, and any image where file size matters and you do not need a transparent background.
PNG uses lossless compression, meaning no quality loss at all. The file is exactly what you put in, just stored more efficiently. PNG supports transparency, which makes it essential for logos, icons, and images that need to sit on top of a colored background. PNG files are larger than JPG files for photographic content, but for graphics with solid colors and sharp edges, PNG compression is actually very efficient.
WebP is Google's format designed to replace both JPG and PNG for web use. It supports both transparency and photographic content, and produces files about 30 percent smaller than JPG at equivalent quality. All major browsers support WebP now. If you are optimizing images for a website, converting to WebP is worth doing.
GIF supports animation and basic transparency but is limited to 256 colors, which makes it unsuitable for photographs. Its main use today is simple animations. For any static image, JPG or PNG will look better at a smaller file size.
BMP is an uncompressed format from early Windows. Files are very large and there is no practical reason to use BMP for anything modern. If you have BMP files, convert them to JPG or PNG.
When you need to convert formats
Converting JPG to PNG is necessary when you need transparency. If you want to remove the background from a photo, you need a PNG to store the transparent areas. JPG does not support transparency at all, so any transparency gets filled with white.
Converting PNG to JPG is useful when you have a PNG photo and want a smaller file for sharing or uploading. If the PNG does not have any transparent areas, converting to JPG at 85 percent quality gives you a significantly smaller file with no visible quality difference.
Converting to WebP makes sense for any image you are putting on a website. The size reduction improves page load times, and the format is now universally supported by modern browsers.
Converting from WebP to JPG or PNG is sometimes necessary for compatibility. Older software, some email clients, and some platforms do not accept WebP files. Converting to JPG solves compatibility issues.
What happens to quality during conversion
Converting from a lossless format like PNG to another lossless format loses nothing. The image is identical.
Converting from a lossless format to a lossy format like JPG introduces some quality reduction. How much depends on the quality setting you choose. At 90 percent, the loss is practically invisible. At 60 percent, it is noticeable on close inspection.
Converting from one lossy format to another lossy format compounds the quality loss. Each generation of lossy compression discards more data. If you have a JPG and convert it to WebP and back to JPG, each conversion step reduces quality slightly. For important images, work from the original source file whenever possible.
How to convert image formats with OnlineToolsPlus
- Open the Image Converter tool below.
- Upload your image.
- Select the output format: JPG, PNG, or WebP.
- If converting to JPG or WebP, adjust the quality setting if needed.
- Download the converted image.
The conversion runs entirely in your browser. No upload to any server, no account needed, completely free.
Convert your image to any format right now. Free, instant, private.
What actually changes when you convert an image format
An image is ultimately a grid of pixels, each with a color value. The format determines how that grid of values is stored, not what the values are. Converting between formats changes the container and the compression method but not necessarily the content of the image itself. However, some format conversions do change the content, which is where people run into unexpected problems.
Lossless formats preserve every pixel exactly. When you convert from one lossless format to another, the image is identical pixel for pixel before and after. Converting between lossy formats is different. Each conversion through a lossy format applies compression again, discarding some data each time. An image that has been saved as JPEG five times has lost considerably more quality than one saved once, even at the same quality setting.
Converting from a lossy format like JPEG to a lossless format like PNG does not recover the lost data. The PNG version will be identical to the JPEG it was created from, not to the original before JPEG compression was applied.
When each format is the right choice
JPEG is appropriate when file size is important and you are working with photographs or realistic images with smooth color gradients. JPEG handles flat colors and sharp edges poorly, producing visible artifacts around them, which is why it is a bad choice for logos, screenshots and illustrations.
PNG is the right choice for images with text, logos, illustrations and anything with sharp edges or flat areas of solid color. PNG compression is lossless so there is no quality degradation. PNG also supports transparency, which JPEG does not, making it necessary for any image that needs to work over different backgrounds.
WebP is a modern format that achieves better compression than both JPEG and PNG at equivalent quality. It supports both lossy and lossless compression and handles transparency. Browser support is now universal among current browsers, making it a solid choice for web images where you control the serving environment.
SVG is different from raster formats in that it stores images as mathematical descriptions rather than pixel grids. This means SVG images scale to any size without quality loss, making them ideal for logos and icons that need to appear at multiple sizes.
Format conversion and file size
The relationship between format and file size is not fixed. A JPEG can be larger or smaller than a PNG of the same image depending on the image content and the compression settings applied. For photographic images, JPEG at moderate quality settings will usually be smaller. For flat-color graphics, PNG often produces smaller files because JPEG's compression algorithm works against the sharp transitions in this type of image.
If file size is your primary concern, test a few different format options and compare the results for your specific content. The format that works best varies by image, and generalizations based on format alone are often wrong for any particular case.
Metadata handling varies by format conversion. JPEG files contain EXIF metadata including camera settings, date and location. When converting from JPEG to PNG, most converters preserve the EXIF data in the output file. When converting from PNG to JPEG, no EXIF data exists to transfer. If preserving or removing metadata is important for your use case, verify how your converter of choice handles it rather than assuming.
Progressive JPEG is a variant of the JPEG format that downloads in multiple passes at increasing resolution. The first pass delivers a low-resolution preview quickly, subsequent passes refine the image progressively. This produces a better perceived loading experience compared to baseline JPEG, which loads from top to bottom. For images displayed in contexts where loading speed is visible to the user, converting to progressive JPEG is a minor optimization with no quality cost.