M3U8 commonly identifies an M3U-style playlist encoded as UTF-8. HLS also uses this playlist format for its streaming instructions. The extension alone therefore does not tell the whole story: the file's contents determine whether it is a general media list, an HLS playlist or something the player cannot interpret.
A practical example
A playlist using accented programme names may be saved with UTF-8 encoding so the characters survive correctly. Another M3U8 file may describe timed HLS segments instead of listing a set of separately named television channels in a catalogue.
A common misunderstanding
Do not rename an incompatible file to M3U8 and expect conversion. Correct text encoding and valid playlist structure are separate requirements from the filename used to save it.
Related terms
Stable technical definition. Editorial approach