Untrunc

Untrunc is a free, open-source tool for repairing damaged or truncated MPEG-4 video files when you have a healthy clip from the same camera and recording settings. It is best suited to people who can supply that reference and are comfortable using a local repair workflow; its narrow format support is the main reason to look elsewhere.

Overview

Untrunc reconstructs missing or damaged index metadata in MP4, MOV, M4V, and 3GP containers. It rebuilds the file structure without re-encoding or altering the raw media, a practical advantage when the underlying video and audio data remain intact. It cannot rescue an empty file or raw media that is itself corrupted, and it does not handle containers such as AVI or MKV.

The reference clip is central to the process: it should come from the same camera with the same recording settings. That makes Untrunc a focused repair option rather than a general-purpose fix for arbitrary broken videos. Repairs run locally and offline, without uploads or telemetry, which suits footage users prefer to keep on their own devices.

Key features

• Container repair: MP4, MOV, M4V, and 3GP are supported. The tool targets container structure and index metadata, not damaged raw video data.
• Reference-based reconstruction: A healthy clip from the same camera and recording settings is required. Users without a suitable sample cannot use the core repair method.
• Large-file handling: There is no file-size limit, and streaming mode can process files larger than available RAM. That avoids a stated memory ceiling, though it does not expand the formats or damage types Untrunc can repair.
• Command line and GUI: The Windows download includes both a command-line tool and graphical interface; other platforms use a command-line workflow. Windows users have a choice of interface, while users elsewhere should be prepared to work at the command line.
• Camera support and audio: The project describes support for GoPro footage and Sony XAVC, with the anthwlock fork adding compatibility and performance improvements. Optional stretch mode can adjust audio duration to match the recovered video track.
• Local, open-source use: Untrunc is GPL-2.0 software, free for personal and commercial use, with offline local-file repairs and no telemetry.

Pricing

Free — free: Download and use the software without license fees or subscriptions. There are no usage or file-size limits, and the GPL-2.0 license permits personal and commercial use. The trade-off is not a quota or seat cap, but the requirement for a healthy reference clip with matching camera and recording settings, plus the supported-container and damage limits.

There is no free trial because the software is free to download and use. Technical support is directed to the anthwlock GitHub Issues page; the informational website does not provide software support.

Platforms

Untrunc supports Windows, macOS, and Linux, and is also categorized as self-hosted. The Windows download offers a graphical interface and command line; the described workflow on other platforms is command-line based.

Who it's for

Untrunc is a sensible choice for action-camera users, drone pilots, dashcam owners, screen recorders, security-camera operators, and videographers whose MPEG-4 footage has damaged or missing index metadata and who can provide a matching reference. Its local processing and lack of file-size limits also suit people handling large clips or footage they do not want to upload.

It is not the right tool for AVI or MKV files, empty files, or footage whose raw media data is corrupted. It is also a poor fit when no suitable reference clip exists or when a non-Windows user needs a graphical workflow.

Pros and cons

• Pro: No usage or file-size limits, with streaming mode for files larger than available RAM, makes it viable for large recordings without a stated quota.
• Pro: Local offline repair without uploads or telemetry keeps footage on the user's device.
• Pro: It repairs container structure without re-encoding or modifying raw media, preserving intact media data.
• Con: The same-camera, same-settings reference requirement can rule it out when no comparable healthy clip is available.
• Con: Support is limited to the anthwlock GitHub Issues page; the informational site does not provide software support.
• Con: AVI, MKV, empty files, and corrupted raw video data are outside its repair scope.

Alternatives

For a broader repair directory, browse File Repair Software or Video Repair Software.

• IntactFile is a better fit for users seeking a multi-category service across web and desktop platforms, but its free tier limits video to three repairs per day and 50 MB per video.
• DiskInternals ZIP Repair is for Windows users repairing ZIP archives of any size, not MPEG-4 video.
• Restore.Media is an option for users who prefer an automatic recovery service across web and mobile platforms; automatic recovery is billed per file at $4.99, paid once, with price varying by repaired file size.
• Recovery Toolbox File Undelete Free is for recovering deleted files from NTFS drives on Windows rather than repairing video containers.
• Remo Repair Word repairs .doc and .docx files on Windows, so it suits document rather than video repair.
• Fix.Video is a paid alternative for users considering file-based video repair; its 10-file plan costs $59, paid once.
• lzip is another free tool available on Linux, macOS, Windows, and self-hosted environments.
• 3-Heights PDF Analysis & Repair Tool is a paid alternative with a free trial for PDF work.

Verdict

Choose Untrunc if you need to repair supported MPEG-4 footage locally, have a matching healthy reference clip, and want an unrestricted free tool that does not re-encode the media. Look elsewhere if the file is an unsupported container, its raw video data is damaged, or you need repair without a suitable reference.