Text expansion: why a faithful line stops fitting
Text expansion is the tendency of a translated sentence to run longer than the original, often by a fifth or more. It breaks a dubbed line against a mouth and a subtitle against a reading limit, and it is not uniform across a script. As of 2026-09-22.
| Kind of line | Expansion | What breaks first |
|---|---|---|
| Short exclamation | Little | Nothing |
| Ordinary dialogue | Moderate | Mouth timing in a dub |
| Explanatory speech | Most | Reading limit in a subtitle |
| On-screen label | Moderate | The space it was drawn into |
Inclusion rule. The kinds of line in a script, ordered by how much a translation typically adds. The figures behind this are properties of language pairs. Order. Least expansion first.
1The extra words gather in exposition
Short exclamations survive translation at about their original length. Explanatory lines are where the additional words accumulate, because that is where a language difference in structure has room to show.
That is a reason to keep exposition out of close-ups in a series planned for several markets. A close-up ties the line to a visible mouth, and exposition is the line most likely to outgrow it.
2Translating for length is a decision made before the audio
A dubbed line that carries the full meaning and no longer fits is not fixed by a better performance. It is fixed by a shorter translation, which has to happen before the audio is made.
So expansion is an argument for making the language decision early. In a pipeline where the line is spoken as the picture is generated, the constraint disappears because nothing was timed to a different sentence.
3It is invisible in every language list
No published figure in this register mentions it. A language appearing in an inventory says a voice exists; it says nothing about whether a line in that language will fit a shot cut for another one.
For a producer the useful move is to check which pipeline a vendor describes. The constraint applies fully to a dubbing pass and not at all to a line generated in the language from the start.
A definition, not a measurement: no vendor figure appears here that is not also in the register. Which vendors describe which pipeline is printed in their voice cells.
Nearby terms: Reading speed, Transcreation. The whole vocabulary is at terms; nothing on this page is a claim about a named product.