A file converter that never uploads your files
Most online converters send your files to a server, convert them there and keep a copy for some time. This one works differently: the conversion runs in your browser, on your own computer or phone. Your photos, class notes and grade spreadsheets are never uploaded, so it works with confidential documents and is often faster than waiting for an upload.
It's also free with no account, no daily limit and no watermark. Once the page has loaded, most conversions even work offline.
The conversions students need most
HEIC to JPG: iPhone photos are saved as HEIC, which many school platforms and Windows apps don't accept. Converting them to JPG makes them readable everywhere.
Images to PDF: photograph handwritten homework page by page, then combine all the photos into a single PDF to hand in. PDF to JPG does the opposite, turning each page of a PDF into an image to insert in slides or notes.
Word to PDF: send your essay in a format that looks the same on every device. Word to Markdown or text is handy to reuse your writing in a notes app.
CSV to Excel and Excel to CSV or JSON: open exported data in a spreadsheet, or prepare a file for a statistics or programming class.
MP4 to MP3 and audio to MP3: keep only the sound of a recorded lecture so it takes far less space and can be played anywhere.
How to compress a PDF, a photo or a recording
Switch to Compress, drop your files and keep the Recommended level: photos are re-encoded at a quality that looks identical on screen and resized to a sensible maximum, which usually makes them 50 to 80% lighter. If a platform imposes a limit, choose a maximum size such as under 1 MB and the tool adjusts quality and dimensions until the photo fits.
Heavy PDFs, like scanned homework or slides full of images, are rebuilt from lighter page images. It is the most effective way to get under an upload limit, but the text of the compressed PDF can no longer be selected, so keep the original for reading and searching. Lecture recordings and videos become compact mono MP3 files, often ten times smaller.
Getting the best quality and the smallest files
For photos, JPG or WebP at 80 to 85% quality is visually almost identical to the original and often five to ten times lighter. Keep PNG for screenshots, diagrams and images with transparency. Reduce the image size to 1920 pixels wide if a platform rejects files that are too large.
When you turn a PDF into images, choose 150 dpi for reading on screen and 300 dpi if you need to print or zoom in on small details. For lecture recordings, MP3 at 96 or 128 kbps in mono is clear and very compact.