Help center

The most common causes, in rough order of how often they happen:

• The file is over 30 MB. The web converter caps inputs at 30 MB to keep memory usage reasonable in the browser. The downloadable local version has no cap.
• The browser ran out of memory mid-conversion. This usually only happens on very long videos or very high-resolution images. Try a smaller file, a lower output resolution, or switch to the local version.
• The source file is corrupted. Open it in its native app first to confirm it works. If it does not, the converter cannot recover it.
• The codec inside the container is unusual. For example, an AVI file containing an old DivX codec, or an MKV with DTS audio. Try the local version, which includes more decoders.
• You are on a very old browser. day2dayfile needs a modern browser with WebAssembly support — Chrome 90+, Firefox 90+, Safari 14+, or Edge 90+ for full functionality.

If none of these explain it, email us with the file type, the browser you are using, and the step that failed.

Memory. The web converter runs everything inside a browser tab, which has a much smaller memory budget than a native app. Loading a 50 MB video file and decoding it in JavaScript can quickly hit limits, especially on phones and lower-end laptops.

The 30 MB cap is a safe ceiling where conversion completes reliably on the widest range of devices. If you need to convert larger files, the downloadable local version has no cap — it can use as much of your computer's memory as the OS will give it.

Images: JPG, PNG, WebP, QOI, and most browser-supported formats including BMP and (on most browsers) HEIC.

PDFs: any PDF that opens in a browser. The PDF tool focuses on merging and splitting; it does not currently render PDFs to images, but that is on the roadmap.

Audio: anything the browser can decode plus bundled decoders — MP3, WAV, OGG, FLAC, M4A/AAC, WebM audio, and most common formats.

Video: MP4, MOV, MKV, WebM, M4V, AVI (most flavors), and others through the bundled FFmpeg WebAssembly build.

Images: JPG, PNG, WebP, QOI, and raw RGBA.

PDFs: a single merged PDF, or one PDF per page when splitting.

Audio: WAV, MP3, OGG (Vorbis or Opus depending on browser), FLAC, M4A/AAC, and WebM audio.

Video: MP4 (H.264), WebM (VP9), MOV, MKV, and M4V depending on the browser's encoding support. WebM uses native browser recording; the others use bundled FFmpeg.

Re-encoding video is computationally heavy work. The browser has to decode every frame of the source, optionally resize it, then re-encode it with the chosen codec. A 1-minute 1080p clip can take anywhere from 20 seconds on a fast desktop CPU to several minutes on a phone.

WebM output is usually the fastest because it uses native browser recording APIs instead of WebAssembly FFmpeg. MP4, MOV, MKV, and M4V are slower because they use FFmpeg in software.

For long videos, the local version is significantly faster because it runs FFmpeg natively rather than inside the browser sandbox.

Yes, for images. Drop multiple files into the image drop zone and they convert in sequence, each with its own download. For PDFs, you can also drop multiple files at once when using the "merge" action.

Audio and video are processed one file at a time because of memory constraints in the browser.

No. The conversion runs locally in your browser. The file is read from your device, processed in memory inside the browser tab, and the result is given back to you for download.

You can verify this yourself: open your browser's DevTools (F12), go to the Network tab, and run a conversion. You will see no outbound request that contains your file data.

No. Display ads are loaded by separate ad-network scripts that have no access to the data you drop into the converter. The ads run in their own sandbox provided by the browser. Your file never enters their world.

If you would rather not see ads at all, download the local version. It contains no ad scripts.

We do not currently use any user-tracking analytics. Our hosting provider keeps short-lived access logs (IP, user agent, requested URL, timestamp) for security and abuse prevention, the same as any web host. Those logs are not connected to your files in any way — they record that someone visited a page, nothing else.

The advertising cookies used by Google AdSense are described in detail on our privacy policy page, including how to opt out.

The web version needs the initial page load (HTML, CSS, the scripts and encoders) before you can use it. After the page is loaded, you can disconnect from the internet and the converter will still work because the conversion runs in your browser, not on a server.

For a truly offline-only experience, download the local version. It is a ZIP that you can unpack and run from any folder on your computer, no internet required after download.

A small ZIP (about 30 MB) containing the same converter that runs on the website, with no ads and no internet dependency. Unzip it anywhere, double-click the included index.html, and the converter opens in your default browser.

The local version has the same features as the web version, but with the 30 MB input file cap lifted.

Go to the download page. There is a short countdown before the download starts, which is how the project funds itself — that page shows an ad while the ZIP becomes available.

Unzip the file. You will see an index.html file alongside the converter scripts. Double-click index.html, or right-click and "Open with" your preferred browser. The converter loads and works exactly like the web version, minus the ads.

On Windows, you may see a SmartScreen warning the first time. That is normal for any new file you have not run before; click "More info" then "Run anyway" once you have confirmed you trust the source.

Not on any schedule. The local ZIP is self-contained. When we ship significant improvements to the conversion code, we update the download. If you want the latest version, re-download the ZIP every few months or whenever you notice the website has new features.

No. There are no paid plans, no premium accounts, and no paywalled features. The website is supported by display ads served through Google AdSense; the local version is free and ad-free.

Ads pay for the project. day2dayfile is built and maintained as an independent project with hosting, development time, and storage costs that need to be covered somehow. The ad slots are clearly labeled and never overlap the converter itself.

If you would rather not see them, download the local version — it has no ad scripts at all.

Visit Google's Ads Settings to turn off personalization across Google services, or aboutads.info to opt out across many ad networks at once. You will still see ads, but they will not be tailored to your browsing history.

For users in the EEA, UK, or Switzerland, we use Google's certified Consent Management Platform to gather consent for personalized ads.

Ads are served by Google's ad network, not by us, so the destination is not something we control. If an ad sent you to something that looks like a scam (fake antivirus warnings, "your PC is infected" pages, fake software downloads), you can report it through the small information icon on the ad itself, or send us the details and we can flag it on our end too.

Any modern browser with WebAssembly support: Chrome 90+, Firefox 90+, Safari 14+, Edge 90+. Brave, Vivaldi, Opera, Arc, and similar Chromium-based browsers work as well.

Older browsers will load the page but may not be able to run the heavier converters (video, audio re-encoding). Image and PDF tools have a better chance of working on older browsers because they use lighter APIs.

Yes, for images and PDFs especially. Audio works but is slower because mobile CPUs are less powerful. Video conversion is technically supported but can be slow and may stress device memory; for long video work, a laptop or desktop is a better fit.

Browser code runs inside a sandbox with restricted CPU usage and memory access. Native desktop apps have no such restrictions and can run multiple CPU cores in parallel without the same overhead. For occasional conversion this is fine; for heavy daily work, a desktop app or our local version (which still runs in a browser but skips network overhead) is faster.