Add Vietnamese Subtitles to a Video

Subtitles carry the whole job

Plenty of tools reach a new language by replacing the voice. For Vietnamese, mydubly doesn't: AI dubbing covers 19 of the 21 languages, and Vietnamese is one of the two without a voice. What does exist is everything on the text side. Vietnamese speech can be transcribed, speech in any of the other 20 languages can be translated into Vietnamese, and both can become subtitles, a transcript or a subtitle file.

That puts more weight on the subtitles than usual. They are not a convenience layered over a dub; for a Vietnamese viewer they are the translation. So the two things this page cares about are the words being right and the marks on those words being readable. If you want the text without the video, Vietnamese video to text produces a transcript, and the Vietnamese video translator page explains what a translated Vietnamese version includes.

How Vietnamese sits on a subtitle line

Vietnamese is written in Latin letters with extra vowel shapes (ă, â, ê, ô, ơ, ư), the crossed đ, and five tone marks placed above or below vowels. A single vowel can carry two marks at once: ấ, ầ, ẩ, ẫ, ậ, or ở and ữ. Each syllable is written as its own word, so a sentence has many short words and plenty of places to break a line.

For the editor's checks Vietnamese counts as a Latin-script language: it warns above 21 characters per second and above 42 characters per line. Short syllables mean wrapping almost never produces awkward breaks; the harder part is vertical space.

Room for stacked marks

Tone marks extend a line both upward and downward. Marks on capitals such as Ấ or Ổ rise above the normal height of capitals, and the dot below in ạ or ộ drops under the baseline. In a two-row subtitle, the dots under the top row meet the marks above the bottom row, and at tight spacing they collide.

• Line height: raise it a step or two in the Style tab. The presets with big, bold text use tighter spacing, which suits English and crowds Vietnamese.
• UPPERCASE: leave it off. Capitals push stacked marks even higher, and all-caps Vietnamese is noticeably harder to read.
• Outline: a thick outline can swallow the dot below and the small hook in ả or ở at modest sizes. A background box, as in the YouTube or High Contrast presets, keeps the marks crisp; so does a thinner outline. Subtitle backgrounds compares the options.
• Size: go a little larger than you would for English. The marks are the smallest details on screen, and they carry meaning.

Choosing a typeface

Vietnamese needs a font designed with its characters in mind, not merely one that has accented Latin letters. Among the bundled families, Noto Sans, Noto Serif, Roboto, Open Sans and Inter are widely used for Vietnamese text and make sensible starting points. With any other face, and especially the display faces, preview before you commit. When a font lacks a letter, the renderer substitutes it from a fallback font, so you won't get empty boxes, but one syllable drawn in a different design stands out in the middle of a word.

A practical test line: "Những người ở Hà Nội thường uống cà phê sữa đá", then a capital line such as "ĐỒNG HỒ". Type them into one subtitle, step through a few fonts, then undo. The guide to subtitle fonts has more on weight and legibility at small sizes.

Getting the words right

For Vietnamese speech, keep "Subtitle language" on auto-detect. Whisper recognises the language and writes Vietnamese with full diacritics. Because Vietnamese has six tones, ma, má, mà, mả, mã and mạ are six different words that differ only by the mark, and a recognition error often keeps the syllable and gets the tone wrong. Read the lines rather than skimming them, particularly where there is music, fast speech or a strong regional accent.

To subtitle a video in English, French, Korean or another supported language, choose Vietnamese in the same menu. Translation has a specifically Vietnamese difficulty: pronouns depend on the relationship between speaker and listener (tôi, mình, anh, chị, em, bạn), and English "I" and "you" carry none of that. Check that the forms fit the people on screen; for a presenter speaking to an audience, bạn is the usual neutral choice. Translated lines are split by text length, so their timing is approximate; nudge starts and ends on the timeline where a line runs ahead of the speaker.

The AI pass costs 1 credit per minute: an 8-minute video is 8 credits (0.8¢), and short clips are billed at the 5-credit minimum.

Example settings

Talking head for YouTube

YouTube preset, Roboto, line height raised a step, bottom position. Export SRT as well for YouTube's subtitle upload.

Vertical clip for Reels or TikTok

Social Media preset with UPPERCASE switched off, Noto Sans, a little extra line height, and the 9:16 safe area visible.

Training or lecture recording

Classic preset with a semi-transparent box behind the text, Open Sans, one row per subtitle where possible.

Video that already has old subtitles burned in

Turn on "Hide subtitles already in the video" to blur that strip, then place the Vietnamese lines over it. The old text is blurred, not erased, and anything else in the band is blurred too.

Where the Vietnamese subtitles go next

The render produces an MP4 with the Vietnamese text in the picture, which plays the same in Zalo, Facebook, YouTube or a classroom projector. Export SRT or VTT from the same session for platforms that accept subtitle files, so viewers there can switch them off; subtitling a YouTube video covers that upload. If a subtitle file is all you need, the subtitle generator and subtitles in another language create SRT or VTT without the styling step.

About the subtitle editor on this page

Opens

MP4, MOV, M4V, WebM, MKV videos your browser can decode

Subtitles from

AI (from the speech, optionally translated into one of 21 languages), an SRT or VTT file, or typing them in

You download

An MP4 with the subtitles drawn into the picture at the original resolution and frame rate, plus SRT and VTT files

Cost

Editing, styling, rendering and SRT/VTT export are free, with no account and no watermark. AI subtitles cost 1 credit per minute (5-credit minimum per video); signing in with Google gives 100 free credits and accounts get 10 free credits a day

Privacy

The video never leaves your device and is rendered in your browser. Only for AI subtitles is the audio sent, over HTTPS, and it is deleted within 30 minutes of delivery

Rendering needs

Chrome or Edge 94+, Safari 16.4+, or Firefox 130+ on a computer. Editing and SRT/VTT export work in any current browser