How to Convert an Image to PNG, JPEG, or WebP in Your Browser

Converting a file from PNG to JPEG looks trivial, and mostly it is. But a handful of things happen silently in every conversion — transparency decisions, dropped metadata, format substitutions — and knowing them saves you from shipping a file that is subtly wrong.

What a conversion actually does

Image Format Converter works in three steps:

1. The file is read into your browser and shown in a preview.
2. Its pixels are painted onto an in-memory canvas at the same width and height the source has.
3. That canvas is re-encoded in the format you picked and offered as a download.

So a conversion is always a full re-encode. Two consequences follow immediately:

• Dimensions never change. This tool does not resize. If you need a smaller pixel size, that is a compression or max-width job.
• Metadata does not survive. The output is built from pixels alone, so EXIF data — camera model, lens, capture date, GPS position, colour profile, thumbnail — is gone. For a photo you are publishing on a site this is usually a benefit (it strips location data), but if you need that record kept, a format converter is the wrong tool.

Because the export is drawn from the very same preview image you see on screen, what you see in the preview is what you download. Nothing is rotated, flipped, or cropped between the two.

Choosing the output format

The selector offers PNG, JPEG, WebP, BMP and GIF. They are not equivalent:

• PNG is lossless and supports alpha (real transparency). Choose it for screenshots, user interface, logos, line drawings, anything with text, and anything that must stay crisp after further editing. Files are large for photographs.
• JPEG is lossy and has no transparency at all. Choose it for photographs where file size matters. Every re-save costs a little quality, so avoid round-tripping a JPEG through JPEG repeatedly.
• WebP is lossy or lossless, supports transparency, and is typically much smaller than an equivalent JPEG. Choose it for anything served on the web to a modern browser. Older software may still not open it.
• BMP is an uncompressed legacy format. Converting from BMP is very useful; converting to it produces enormous files for no benefit.
• GIF supports only 256 colours and a single-bit transparency (hard edges, no soft shadow). It is worth converting to only when you specifically need a tiny indexed-colour graphic. Animated GIFs lose their animation — the canvas holds one frame, so the output is a still image.

A rough rule: photographs go to JPEG or WebP, graphics with text or transparency go to PNG or WebP, and everything else is a compatibility question.

The BMP and GIF trap

Browser canvas encoders are not required to support every format. When you ask for a type a browser cannot encode, it quietly substitutes PNG instead — the download simply comes out as a PNG.

The file you download is named from the format the browser actually produced, so the extension tells you the truth even when the "Output Format" readout on the page reflects only what you selected. Check the extension of the downloaded file if you specifically needed BMP or GIF, and expect a PNG on some browser and format combinations.

Transparency

Whether alpha survives depends entirely on the target format:

• PNG → PNG, PNG → WebP: transparency is kept.
• PNG → JPEG: there is no alpha channel in JPEG, so the transparent areas are filled in by the browser. This page does not let you choose the matte colour, and different browsers default differently. Do not rely on it. If you need a specific background behind a transparent image, either set the background in CSS or composite it onto the colour first.
• JPEG → PNG: the JPEG's opaque rectangle is preserved; you do not gain transparency by converting to PNG. Alpha is something you create by erasing pixels in an editor, not by changing format.

A common mistake is converting a logo JPEG → PNG "to get transparency". The file gets bigger and stays opaque.

When quality drops

Conversion never improves an image. A JPEG with compression artefacts converted to PNG keeps those artefacts at full size — you pay the byte cost of PNG without recovering the lost detail. Lossy → lossy (JPEG → WebP) compounds the damage, which is why the intermediate should be as high quality as possible.

The sensible order of operations is: edit at full quality, resize, then encode for delivery — and always as the last step before publishing.

After converting, check three things

1. File size. If it grew, you probably converted a photograph to PNG or a compressed file to BMP. Switch format or use compression.
2. The edges. Zoom to 100% on a text-heavy area or a logo edge. JPEG handles flat colour boundaries badly — if it looks fuzzy, PNG or WebP is the right target.
3. Transparency. Open the result over a dark background. If you expected transparency and got white or black, the target format cannot carry it.

Bulk work

Converting dozens of files one at a time is the wrong tool for the job. Image Batch Processing takes PNG, JPEG and WebP files in one go, resizes them by pixels or percentage, and hands back a ZIP — with a format selector and the option to flatten transparency onto white for JPEG output.

Privacy

Everything above happens inside your browser tab: the file is read locally, the canvas is local, and the encoded result is written locally. Nothing is uploaded, which is why the conversion works with no account and no queue — and why it also works on a plane. The only network traffic on the page is the analytics and advertising scripts it loads, not your image.

Related guides

• How to compress an image without making it worse — quality, max width, and when compression backfires
• Batch resize and convert images: what to know first — many files at once, with a ZIP at the end
• How to stitch screenshots into one long image — combining files rather than re-encoding them