You drag a file into the tool and nothing happens, or you get an error about the format. This guide covers the most common reasons and the concrete fix for each one.
The underlying cause is almost always the same: browser-based tools can only open files that the browser itself can decode. The browser has a built-in image decoder for JPEG, PNG, WebP, GIF, and BMP. Anything else — HEIC, RAW, TIFF — requires a native OS codec that the browser has no access to, regardless of whether that codec is installed on your system.
HEIC and HEIF — iPhone photos
Since iOS 11 (2017), iPhones shoot in HEIC by default. HEIC uses the same compression as H.265 video, which is why a 12 MP iPhone photo is often just 2–4 MB — impressive compression for the quality. The catch is browser support.
As of 2025, HEIC decoding in browsers works reliably on:
- Safari on macOS and iOS — Apple built in HEIC support natively
- Chrome and Edge on macOS — delegates to the macOS HEIC codec
It does not work reliably on:
- Chrome and Firefox on Windows — needs the HEVC Video Extensions codec from the Microsoft Store (it was free, then it wasn't, and availability varies)
- Chrome and Firefox on Linux — no system codec available
- Android browsers — inconsistent support depending on Android version and vendor
Fix: change your iPhone's camera format
On your iPhone, go to Settings → Camera → Formats and choose "Most Compatible." Your camera will now shoot JPEG instead of HEIC. This is the most reliable fix if you regularly need to process photos on non-Apple systems.
If you need to convert existing HEIC files, the easiest route on a Mac is to open them in the Photos app and export as JPEG. On Windows, the built-in Photos app can open HEIC files if you have the right codec, and you can use "Save as" to convert. Alternatively, AirDrop to a Mac and convert there.
Camera RAW files — CR2, NEF, ARW, DNG, and others
RAW files from digital cameras (Canon's CR2/CR3, Nikon's NEF, Sony's ARW, Fuji's RAF, Olympus's ORF, the universal DNG) contain unprocessed data directly from the camera sensor. They are not images in the conventional sense — they're raw sensor readings that require a RAW processor to apply demosaicing, white balance, and tone curves before you get a viewable image.
No web browser can decode RAW files. There is no workaround: RAW processing requires dedicated software. You need to export from the RAW file first.
Fix: export from your photo software
- Adobe Lightroom / Adobe Bridge: File → Export → JPEG or TIFF
- Apple Photos (macOS): File → Export → Export [n] Photos as JPEG
- Windows Photos: Open the RAW file (requires a camera-specific RAW codec, often available from your camera manufacturer), then Save As JPEG
- Capture One, darktable, RawTherapee: all support exporting to JPEG or PNG
Once you have a JPEG or PNG export, you can bring it into this tool to compress further or convert to WebP.
BMP — technically fine, but huge
BMP (Windows Bitmap) files are supported by browsers and by this tool — you can drag one in and it will open. The issue is just that BMP is essentially uncompressed: a 1920×1080 BMP file is around 6 MB, compared to a few hundred kilobytes for the same image as a JPEG or WebP.
If you have a BMP, opening it in this tool and converting to JPEG or WebP at 80% quality will typically shrink it by 90–95%. That's the point.
Very large files
Files over 50 MB are rejected before decoding. This is a practical limit — very large images can exhaust browser memory during the canvas operations needed to re-encode them.
Images with very high megapixel counts — above 80 MP — are automatically scaled down to fit within safe canvas limits before encoding. You'll still get a useful output, just not at the full original resolution. This only applies to unusually large images; most photos from consumer cameras are well under 50 MP.
If you're working with truly huge images (medium format, panoramas, scans), you'll need dedicated desktop software like Photoshop, GIMP, or ImageMagick, which can handle much larger canvases than a browser tab.
GIF files
GIF files open correctly, but the tool exports them as a single still frame — whichever frame is first. There's no support for preserving animation, because the Canvas API doesn't provide access to individual frames of an animated GIF in a straightforward way.
If you need to work with animated GIFs, you'll need a dedicated tool. If you need to convert a static GIF to a smaller format, this tool handles that fine: drop it in and export as WebP or JPEG.
TIFF files
TIFF is a complex container format — it can hold multiple images, multiple compression types, floating-point data, and more. Browser support is limited and inconsistent. Most browsers cannot decode TIFF at all. If you have a TIFF from a scanner or professional camera workflow, open it in your photo editing software first and export as JPEG or PNG before using a browser-based tool.
Corrupt or truncated files
If a file was only partially downloaded, corrupted during transfer, or saved incorrectly by another application, the browser won't be able to decode it. You'll see an error about the file not being readable. The fix is to get a fresh copy of the file from the source.
This sometimes happens with images shared through messaging apps that apply aggressive compression or change the file extension without properly re-encoding the file.
If an image won't open in the tool, try opening it in your operating system's built-in image viewer first. If it won't open there either, the file is likely corrupt. If it opens fine, the format probably isn't supported by your browser's decoder.
For a broader look at which formats work best for different use cases, see JPG vs PNG vs WebP.
JPG, PNG, WebP, GIF, and BMP — drop them in and convert or compress instantly.