图片 转 JPG 转换器

The usual situation is a pile of images from different places: PNG screenshots, WebP pictures saved from websites, HEIC photos from an iPhone, an AVIF or two, and a portal that accepts only .jpg. Rather than finding a separate converter for each, add them together. Each file is identified by its first bytes, not just its name: HEIC goes through a WebAssembly build of libheif, ICO files have their largest icon extracted, and everything else is decoded by the browser’s own image engine before being drawn to a canvas and saved as JPEG.

Up to 30 files fit in one drop, 50 MB each, and you can add more before converting. Each file converts on its own, so one unreadable image shows an error without stopping the rest.

JPG is lossy, so the slider (10% to 100%, starting at 90%) sets how much detail is traded for size. At 90% most photos look unchanged at full size; 75–80% is usually enough for a web upload with a 1 MB or 2 MB cap; below 60% blocky artefacts start to show in skies and around text. As a rough guide, a 2–3 MB PNG screenshot of a 1920×1080 screen often comes out at a few hundred KB at 80%.

If the source is already a JPG, it is re-encoded at the chosen quality rather than copied, which helps when you want it smaller but costs a little detail. To change only the extension of a .jpeg or .jfif without re-encoding, use the JPEG to JPG or JFIF to JPG pages instead.

JPEG has no transparency, so transparent pixels in a PNG, WebP, GIF, SVG or ICO are filled with white; a logo on a transparent background becomes a logo on a white box. It also stores a single frame, so an animated GIF or WebP gives you its first frame. SVG files are rasterised at their declared size with the longest side capped at 4096 px, and drawn at 1024×1024 when the browser reports no size for them. HEIC extras such as Live Photo motion and depth maps are dropped. The output carries no EXIF data, because the canvas writes fresh pixels, although a JPEG with an EXIF rotation flag is drawn upright first.

When any of that matters, keep the original, or convert image to PNG for a lossless file that keeps transparency.

Nothing you add here is uploaded. Files are read into your browser’s memory, decoded and encoded there, and returned as downloads, one by one or bundled into a ZIP. The HEIC decoder is only fetched when a HEIC file is actually converted, so a batch of PNGs never waits for it. That makes the page suitable for ID scans, signed forms and personal photos that a portal wants as JPG.