What MPEG to MP4 actually writes
Old .mpeg and .mpg files from cameras and DVDs fail on phones.
The clip is re-encoded to a normal MP4. The first run downloads the converter.
Quality and the MPEG file you should keep
DVD menus, extra angles, and subtitle pictures are not kept. You get one picture and one audio stream.
A related step, if you still need one, is MP4 to MPEG.
When MPEG to MP4 is the right page
MPEG to MP4 sits on this site because MPEG and MP4 are not interchangeable, even when they look similar in a file list. Old .mpeg and .mpg files from cameras and DVDs fail on phones. DVD-like hardware and old cameras are the usual source. Websites and phones want MP4. Phones, browsers, Instagram, YouTube, and WhatsApp all expect MP4.
The clip is re-encoded to a normal MP4. The first run downloads the converter.
What you give up by leaving MPEG
MPEG covers older .mpeg and .mpg files. Players are inconsistent, which is why MP4 replaced them. Menus, extra angles, and picture subtitles from a DVD are not kept.
Keep the MPEG or the disc copy until you have watched the MP4.
What you gain, and do not gain, with MP4
The download has to be MP4, because that is the format the next step named. Phones, browsers, Instagram, YouTube, and WhatsApp all expect MP4. If the other person can open only one video format, MP4 is that format.
A new encode cannot look cleaner than the MP4 you started with. A remux on a desktop is the lossless path when the streams are already compatible.
A test that matches the real file
Start from the question the other software asked. If it asked for MP4, MPEG to MP4 is the matching page. If it asked for something else, switch tools instead of hoping a similar extension will pass. Old .mpeg and .mpg files from cameras and DVDs fail on phones. The clip is re-encoded to a normal MP4. The first run downloads the converter. The limit is the part people skip, and it is the part that decides whether the download is usable. DVD menus, extra angles, and subtitle pictures are not kept. You get one picture and one audio stream. The file stays on your device. The first run downloads a converter, so keep this tab open. A phone runs out of memory on long files. A computer is the safer place for a big clip. Check three things in the download: it opens, the MPEG material you cared about is still there, and the file size or the layout is what the form described. A new extension alone is not those three things. If a portal, a teacher, or a client rejects the file, send them the original MPEG as well when you are allowed to. MPEG to MP4 is a convenience copy. It is not a new master. Video files hide the real problem inside the container. MPEG to MP4 re-encodes on your device. It does not silently copy every audio language and every subtitle the way a desktop remux can. If you needed those extra tracks, this download is the wrong result even when the picture plays. Convert a one-minute piece before a full movie, and stay on the tab while the converter downloads the first time.
Here is the decision for MPEG to MP4. You start with MPEG and you stop when a real program accepts MP4. Re-encoding to MP4 makes the clip ordinary and playable. Soft subtitles such as ASS or PGS, and extra audio languages, are awkward or dropped when a tool re-encodes. If those two sentences describe a tradeoff you do not want, do not convert. Renaming the extension by hand will not do this job. Running the tool twice on its own output will not do it either.
DVD menus, extra angles, and subtitle pictures are not kept. You get one picture and one audio stream.
A related step, if you still need one, is MP4 to MPEG.
Other jobs start from the homepage, where each tool is named for the conversion it actually does.