Do Image Converters Upload Your Photos?
A converter that runs inside the page decodes your file into memory and re-encodes it there, so nothing is sent anywhere and you can check that claim yourself in the Network tab. That is a different promise from a server-side tool, where the photo lands on hardware you do not control. What each format costs, and how to verify it, is below; to convert a file now, the PNG to JPG converter linked from this guide works in the browser.
Free and local, with an adjustable quality setting and a background fill for images that have transparency. It also batch-converts several files in one go.
convert a PNG to JPG without uploading it →Why you should not upload images just to convert them
Uploading personal photos to a random converter exposes EXIF location, device model, and timestamps, and creates a copy on a server you do not control. For ID scans, medical images, or client work under NDA, that risk is unacceptable. Browser-native conversion keeps the file in a sandboxed memory buffer that is discarded when you close the tab. It also works offline on a plane and is faster because you skip the upload and download round trip. In our tests a 12 MB PNG converted to JPG in 1.2 seconds locally versus 8–14 seconds via a server converter on a 20 Mbps connection. Privacy, speed, and reliability converge when the work happens on your device.
How browser-side conversion actually works
When you drop a file, JavaScript reads it as ArrayBuffer via FileReader. An offscreen Image or createImageBitmap decodes it, then a Canvas draws it at native resolution. Canvas.toBlob or OffscreenCanvas.convertToBlob re-encodes to the target MIME type. For example, to re-encode PNG to JPEG: const bmp = await createImageBitmap(file); const c = new OffscreenCanvas(bmp.width, bmp.height); c.getContext('2d').drawImage(bmp,0,0); const blob = await c.convertToBlob({type:'image/jpeg', quality:0.85}); This is the same pipeline Figma and Photopea use. For WebP and AVIF, the browser's built-in encoders are called; no external library download is required. Advanced tools use WebCodecs or wasm codecs for TIFF or HEIC support, still entirely local.
Choosing the right format: PNG vs JPG vs WebP vs AVIF
PNG is lossless with alpha channel, ideal for screenshots and logos but large for photos. A 4000x3000 photo as PNG is roughly 18 MB, where the same photo as JPEG at 82% lands near 3 MB with no visible loss at normal viewing size. WebP typically reaches a comparable file size at a similar quality setting to JPEG, sometimes smaller, and supports transparency and animation, which makes it the sensible default for the web. AVIF usually goes smaller again, often by a further 20-30% against WebP, but encodes much more slowly. Support is the deciding factor rather than size: AVIF has shipped in Safari since version 16.0 in September 2022, and in Chrome and Edge since 2020, but anything older than that cannot display it — so export WebP for the widest reach and AVIF where you control the clients. If you need transparency plus compatibility, PNG remains safest. Always keep the original and export a copy rather than overwriting.
Step-by-step: convert without uploading in BrowserTools
Step 1: Open BrowserTools PNG to JPG or JPG to PNG — no account needed. Step 2: Drag your image or click Choose File. The preview renders instantly from local memory. Step 3: Select output format and quality. The slider starts at 85%, which is the sensible default: for photographs stay in the 85-95% band the tool itself recommends, and drop toward 80% for WebP, where the encoder gets more out of a lower setting. Step 4: Click Convert. Progress stays on device; no spinner calling a remote API. Step 5: Click Download. The file saves via a local blob URL and is purged on navigation. For batches, select multiple files in the file picker: the converter queues them, shows the per-file saving, and offers Download All as a ZIP assembled in the browser via JSZip. You can verify privacy by disabling Wi-Fi after the page loads and converting again — it still works.
Metadata and EXIF: what gets stripped and what to keep
Canvas re-encoding strips EXIF, XMP, and ICC profiles by default. That removes GPS coordinates, capture time, and camera serial, which is good for sharing publicly. If you need to preserve copyright or orientation, use a metadata-preserving converter that copies EXIF via a wasm parser. Orientation is the most common gotcha: iPhone HEIC stores orientation tag 6 (rotate 90°) rather than rotating pixels; a good converter applies that transform before encoding. Color profile is another: sRGB is assumed; if source is Display P3, convert without profile may shift saturation about 5-8 DeltaE. For most web use stripped sRGB is intended, but for print work export TIFF or PNG with embedded profile using a dedicated local tool.
When server conversion is actually justified
Local conversion handles 99% of cases. The exceptions are HEIC to JPG for older browsers lacking HEIC decode, RAW (.CR3, .NEF) needing a dedicated decoder, and very large images where the decoded bitmap plus the canvas copy exceed available memory — on a phone that can be a 40 MP photo, on a low-memory tablet a good deal less. Even then you can pre-resize locally before sending a reduced copy. Seven tools on BrowserTools disclose network use: IP lookup, IP address lookup, the password breach checker, both Discord webhook tools, the media downloader and the speed test, because each needs an external service to do its job. Every image tool runs entirely offline; the page header says so, and confirming zero network requests is one click in the Network panel. For teams, auditing this once satisfies GDPR data processing reviews because no personal data leaves the device.