Most downloads will be in .srt (SubRip) format, which is widely compatible with players like VLC and Plex.
For a rip like the one you mentioned, you should look for subtitles tagged with SPARKS or BLOW , as these are the most common scene releases for that specific 1080p x264 encode. Popular platforms where you can find these include: subtitle The Martian 2015.1080p.x264.Bluray-Har...
Ensure you match the subtitle to your movie version. The Extended Cut (approx. 151 minutes) has different timing than the Theatrical Cut (approx. 144 minutes). If the text appears on screen too early or too late, you likely have a mismatch between these versions. Most downloads will be in