Free online PART to ISO converter

What the PART format is

.part is generally a temporary filename used for an unfinished download rather than a complete, standardized file format. Mozilla Firefox and some download managers append .part while saving a file; peer-to-peer applications may also keep incomplete downloads with this extension. The file can contain the beginning or another incomplete portion of an ISO, archive, video, or other file.

The filename does not identify the original format or guarantee that the contents are usable. A download that finished but retained the suffix may already contain a complete ISO, but an interrupted download remains invalid until the original program resumes it.

What the ISO format is

An .iso file is an exact sector-by-sector image of an optical disc or a disc-like filesystem. It can preserve boot information, filesystem metadata, directories, and files in one image.

ISO images are used for operating-system installation media, software distribution, virtual machines, archival copies, and disc burning. Windows, macOS, and Linux can mount many ISO images directly; writing one to a disc or USB device requires software that supports image writing rather than ordinary file copying.

How to actually convert PART to ISO

1. Identify the program that created the file. Reopen the original download page or torrent, then resume the download in that program. Do not rename an unfinished file; the download client may need its temporary name and metadata.
2. Wait until the program reports completion. Check the expected size and, if the distributor provides one, compare the SHA-256 checksum.
3. If the completed file is still named something such as ubuntu.iso.part, close the downloading program and rename it to ubuntu.iso. Renaming changes only the filename; it does not convert or repair data.
4. Test the result before using it. In 7-Zip, open the file and use Tools → Test. On Linux or macOS, run sha256sum image.iso or shasum -a 256 image.iso; on Windows, run certutil -hashfile image.iso SHA256. Compare the output with the publisher’s checksum.
5. Mount the verified image or write it with an ISO-capable tool. A bootable installer must be written using an image-writing function, not copied as a single ordinary file to the destination USB drive.

You can also try the free converter on 101convert.com without installing software. Upload the file only after the download is complete and select ISO as the output when the service recognizes the input; an incomplete .part file cannot produce a valid ISO.

Quality and compatibility limitations

There is no generic PART-to-ISO transformation because .part describes download status, not data structure. If the source download is incomplete, the only reliable fix is to resume or restart it from the original source. If a completed file fails checksum or mounting tests, obtain it again rather than repairing it by changing the extension.

Some download managers store recovery information beside the temporary file or use a name without the original extension. In that case, resume the download first; guessing the final extension or forcing a converter to read the file can discard the metadata needed for recovery.