A caption in English, Spanish or Ukrainian will be read by people for whom it is a second language, and by translation tools that handle some things badly. Writing so that both cope is not dumbing down; it is the same discipline as writing for a scroll.
What travels well
- Short sentences with one idea each.
- Common words: “use” over “utilise”, “start” over “commence”.
- Concrete nouns and verbs: what happened, who did it, where.
- Numbers and dates written so they cannot be misread. “3 March” cannot be read as the other way round.
What does not
- Idioms. “Hit the ground running” becomes nonsense in a translation tool.
- Puns and wordplay. They depend on the sound of one language.
- Long chains of clauses joined by commas.
- Local references that need a local explanation.
A habit that helps
Read the caption aloud in your head once, then cut every sentence by a third. Where you would write a figure of speech, write what you mean. If a joke is the whole point, keep it and accept that it will not travel; if it is decoration, drop it.
The translate button
Most networks offer a translate option under a caption, and it works best on the plain sentences above. It will not rescue a caption that is a pun from start to finish.
Run your own caption through a free translation tool. If the result is odd, the original was harder than it looked.