WebP, JPG, and PNG: Which File to Keep

Pick the file by what the picture has to survive, not by which extension sounds modern. A photograph that will be emailed can be a JPEG. A logo that sits on a colored button needs an alpha channel, so it should stay a PNG or become a WebP that still has one. A hero image on a site that already serves WebP can leave JPEG behind, as long as you still have a master you can re-export. CaseSwitch converts those pairs in the browser. The converters do not all treat transparency the same way, and that difference is the useful part.

The short choice

• JPEG (JPG): photographs and other opaque pictures. No transparency. A second save can add more compression damage.
• PNG: graphics, screenshots, and logos when you need sharp edges or a transparent background. Often larger than a photo-style JPEG of the same pixels.
• WebP: a web delivery format that can be opaque or transparent. Smaller than PNG for many graphics, and often smaller than JPEG for photos, if the page that receives the file accepts WebP.

Those three sentences are the whole decision when you already know the destination. The rest of this guide is what goes wrong when the destination and the file disagree, and which CaseSwitch page matches which disagreement.

What each format actually stores

JPEG stores a photographic compression of opaque pixels. It was built for camera pictures, where a little error in a smooth sky is cheaper than a huge file. It has no slot for “this pixel is see-through.” If a design tool offers to export a logo as JPEG, the checkerboard you saw in the editor becomes white, black, or some other matte in the file. You cannot turn that matte back into transparency later. The information is gone.

PNG stores pixels more directly. It can be lossless, and it can include an alpha channel. That is why interface icons, screenshots with a shadow, and logos with a cut-out shape are usually PNG. The cost is size. A photograph saved as PNG is often several times larger than a reasonable JPEG of the same frame, and it does not look meaningfully better once the camera file was already JPEG. Wrapping a JPEG in PNG does not remove blockiness. It only changes the container.

WebP can go either way. It can be a lossy photo-style file, or a file that still has transparency. Browsers that people actually use in 2026 decode it. Some email clients, some print workflows, and some older CMS upload boxes still refuse it. When they refuse it, you need a JPEG or a PNG, not a lecture about the format. Keep the WebP if you might export again. Do not delete the only master after one conversion.

Transparency is the fork in the CaseSwitch tools

The image tools share one canvas path. A file is decoded, drawn, and written out with toBlob. JPEG output is the special case. Before the image is drawn, the canvas is filled with a background color, because the JPEG encoder cannot store alpha. WebP to JPG and PNG to JPG both set that fill. The default fill is white. If the logo will sit on a black header, white fringe around the old transparent pixels will show. Switch the background before you download, and look at the result on the real page color.

PNG to WebP does not prefill the canvas. The PNG’s alpha plane is still there when the browser encodes WebP. WebP can keep that plane. “Can” is the honest word: confirm the download on a contrasting background. A tiny indexed PNG sometimes does not shrink at all. Compare the byte sizes instead of assuming the newer extension won.

JPG to PNG does not invent transparency. A JPEG never had an alpha channel, so the PNG is opaque. People reach for this conversion when a form rejects .jpg. The form gets a PNG. The picture does not become a cut-out logo. JPG to WebP is the same story for alpha: the source had none, so the WebP is opaque. It can still be a smaller photo. It cannot grow a transparent background that was never in the file.

WebP to PNG is the path that keeps a transparent WebP editable in tools that want PNG. It is also how a lossy WebP becomes a larger file without a second JPEG generation. The PNG will not look like a raw camera file. It will look like the WebP you started with, stored differently. If the WebP was already soft, the PNG stays soft.

Quality, text, and a second lossy pass

The quality control on these converters defaults to 0.92 and is limited to the range 0.1–1. At 0.92 a photograph is usually hard to tell from the source at screen size. Flat color, small text, and one-pixel UI lines are less forgiving. JPEG and lossy WebP both approximate those edges. If the letters in a screenshot grow a halo, raise quality or keep the PNG. Dropping quality to 0.6 to hit an email limit is a visible choice, not a neutral one. Look at the text before you send it.

WebP to JPG can be a second lossy generation. If the WebP was encoded from a JPEG, you are compressing an already compressed picture. Fine detail and gradients suffer more than they would from a single encode off a master. Keep the earlier file when you still have it. The converter cannot recover detail that the previous encode discarded. PNG to JPG has the same one-way character: the JPEG is a smaller opaque picture, and the PNG remains the master if you still need the cut-out.

Screenshots versus photographs

A camera photo wants JPEG or a photo-style WebP. A screenshot of a settings panel wants PNG, or a WebP that you have checked at a high quality. The screenshot is full of flat color and text. That is the case where “make it a JPG” produces ringing around letters. If the destination only accepts JPEG, use a higher quality and accept a larger file. If the destination accepts WebP or PNG, do not force JPEG just because email used to require it.

Animation and metadata

These tools draw one canvas. An animated WebP or an APNG is not a frame list you can step through. You get a still image, not a movie with a frame picker. If the motion matters, use a tool that reads the animation. Do not assume the download contains every frame.

The new file is the canvas pixels. The encoder does not copy the original container’s metadata. GPS coordinates, camera model, and capture time that lived in the source are not written into the download. That is a consequence of drawing and re-encoding, not a separate “strip EXIF” switch. If you need the location tag, keep the original file. If you wanted the location tag gone before you posted a photo, the canvas path does that by not carrying the tag across. It is not a forensic wipe of every backup you already uploaded somewhere else.

Size limits, and when the file will not shrink

Raster uploads over 15 MB are rejected in the browser, before conversion. SVG uploads over 5 MB are rejected. The cap is a device limit so a tab does not die on a giant decode. It is not a queue and it is not a paid tier. If a file is over the cap, resize or crop it locally first, then convert.

A new extension is not a guarantee of a smaller file. A 32-pixel PNG that is already a handful of colors can be smaller than the WebP the canvas writes. A JPEG wrapped as PNG usually grows. Measure the download. If it is larger and you did not gain transparency or compatibility, keep the source.

Which page to open

• WebP to JPG — the destination rejects WebP and the picture can be opaque. Set the matte if the WebP was transparent.
• PNG to JPG — same flatten, starting from PNG. Use it for photos that were saved as PNG. Do not use it for a logo that must float on more than one background.
• WebP to PNG — you need a PNG, or you need to keep transparency for an editor that will not open WebP.
• PNG to WebP — you are shipping a graphic on the web and you want a smaller file that can still be transparent.
• JPG to WebP — you are shipping a photo and the page accepts WebP. Alpha will not appear.
• JPG to PNG — a pipeline demands a PNG extension. The picture stays opaque.
• SVG to PNG — the asset is a vector and the destination wants pixels. Outline text that depends on a font the canvas will not load.

Start with WebP to JPG when a form or a mail client rejects the file you already have.

Use PNG to WebP when the graphic needs to stay transparent and the page can take WebP.

Use PNG to JPG only after you have decided the background color that will replace transparency.

Worked decisions

A product photo for email

The source is a WebP export from a shop theme. The recipient’s client saves it as a blank icon. Open WebP to JPG, leave quality near 0.92, and download. If the product was shot on white, the default matte matches. If it was a cut-out on transparency, choose the background that matches the email, or switch to WebP to PNG and accept a larger file. Do not flatten onto white and then drop the JPEG on a dark template.

A logo

Keep the SVG or the PNG master in the design file. For the website, PNG to WebP is the candidate, after you look at the edges on both themes. For a partner who only accepts JPEG, PNG to JPG is a delivery copy, not the new master. Write down which background you flattened onto. The next person who places that JPEG on a different color will otherwise think the logo grew a white box by itself.

A screenshot of the interface

PNG is the safe archive. If the doc site is slow, try PNG to WebP at 0.92 and read the small type in the picture. If the type fringes, stay with PNG. JPEG is the wrong default for this kind of image even though it is the format people name first.

A phone photo that was saved as PNG

The PNG is large because a photo does not need a lossless container. PNG to JPG, or JPG to WebP if you still have a JPEG, is the shrink path. You will not get transparency, and you should not expect to. Delete nothing until you have opened the new file at 100 percent and looked at faces and fine pattern, not just the thumbnail.

What this guide will not decide

There is no score for a best format. WebP is not a ranking trick. A page does not move in search results because an image changed extension. These converters are not a batch zip tool, they do not resize to a pixel width, and they do not offer a frame picker. SVG conversion is a rasterizer with a script check, not a full SVG sanitizer for every hostile file. If the sentence you needed is not in the list above, the tool does not do that job.

The same limits are recorded, with the file caps and the randomness notes for other tools, on the How we test page. If a tool page and this guide ever disagree, the processor is the one to trust, and the sentence should be fixed.

The build record is How we test.

A compact matrix

Read across. “Alpha after” is what the CaseSwitch canvas path does today, not a promise about every other website’s converter.

• WebP to JPG — alpha is flattened onto the chosen background. Lossy if the WebP was already lossy. 15 MB cap.
• PNG to JPG — alpha is flattened onto the chosen background. The PNG should stay the master if you still need the cut-out.
• PNG to WebP — canvas is not prefilled. Alpha can remain. Compare bytes on tiny icons. 15 MB cap.
• JPG to WebP — opaque in, opaque out. Often the shrink path for photos. No new transparency.
• WebP to PNG — keeps the decoded pixels, including alpha when the WebP had it. File may grow. Detail does not return.
• JPG to PNG — opaque PNG. Use it when the extension is the requirement. Do not expect a restored original.

If you only remember one rule, remember the matte. Transparency does not survive a trip through JPEG, and the color you choose is now part of the picture. Everything else in this guide is a reason to look at the downloaded file before you throw the source away.