SRT Subtitles Explained: How to Add Captions to Your Videos

An SRT file is a plain-text subtitle file. It lists numbered captions, each with a start time, an end time and the words to show on screen. Video players and platforms read it and display the right line at the right moment. Because it's just text, you can open it in any editor, fix a typo or adjust a timing, and upload it to most video platforms. This guide explains the format, shows how to edit it and covers how to add captions to your videos.

What's inside an SRT file

An SRT file is made of blocks separated by a blank line. Each block has three parts:

1. A sequence number, starting at 1.
2. A timing line: start time, an arrow, then end time.
3. One or two lines of caption text.

Here's a short example:

1
00:00:00,000 --> 00:00:03,200
Welcome to the first lesson.

2
00:00:03,200 --> 00:00:07,900
Today we'll set up your account and connect your first project.

3
00:00:08,400 --> 00:00:11,000
Let's get started.

Timestamps use the format hours:minutes:seconds,milliseconds. Note the comma before the milliseconds; that's specific to SRT and a common source of errors when people edit files by hand.

Why captions are worth adding

Captions make video usable in more situations and for more people:

• Accessibility. Viewers who are deaf or hard of hearing rely on captions.
• Sound-off viewing. Many people watch video in public or at work without sound.
• Clarity. Technical terms, names and numbers are easier to follow when you can see them.
• Language learners. Reading along helps viewers who are watching in a second language.
• Searchable text. Platforms can read caption text, which describes what your video says. That doesn't guarantee any ranking, but it gives the platform accurate information about your content.

Readable captions follow a few simple conventions: keep each line reasonably short, avoid splitting a phrase awkwardly across two lines, and leave each caption on screen long enough to read comfortably. Fast narration with long sentences makes this hard, which is another reason to write short sentences in the first place.

For courses and training, captions are often part of accessibility requirements. Check the standards that apply to your organization or platform.

How VoiceoverWise creates subtitles

Every voiceover clip you generate in VoiceoverWise comes with an SRT file timed per sentence. The timings are estimated from the generated audio, not aligned word by word. In practice, that means each sentence appears as one caption at roughly the moment it's spoken, which is a solid starting point for most videos.

Because the timing is per sentence, how you write the script shapes your captions. Short sentences produce short, readable caption lines. A 40-word sentence will produce a caption that's hard to read in the time it's on screen. Our guide to writing scripts for text-to-speech covers sentence length in more detail.

If you already have audio and a script from elsewhere, the free SRT subtitle generator can create a starter SRT file from your text and an estimated duration.

Editing an SRT file

You can edit an SRT file in any plain-text editor. A few rules keep it valid:

• Keep the structure. Number, timing line, text, blank line. Don't remove the blank lines between blocks.
• Keep the timestamp format exact. Two digits for hours, minutes and seconds, a comma, then three digits for milliseconds.
• Avoid overlaps. Each caption's start time should be after or equal to the previous caption's end time.
• Two lines maximum per caption. If a caption is too long, split it into two blocks and divide the time between them.
• Save as UTF-8 plain text with the .srt extension, especially if your captions include accented letters or non-Latin scripts.

Common edits include splitting a long sentence into two captions, shifting all timings if you added an intro to the video, and fixing names that should be capitalized differently on screen than they're spelled in your pronunciation dictionary. Remember that the dictionary changes how a word is spoken; your on-screen captions should still use the correct written spelling.

Adding captions to your videos

YouTube: in YouTube Studio, open the video, go to the subtitles section and upload the SRT file as a subtitle file for the right language. You can then review it in YouTube's editor. Exact menu names change from time to time.

Video editors: most editing applications can import SRT files as a caption track. That's useful if you want to style the captions or burn them into the picture.

Social platforms: some accept SRT uploads; others generate their own captions or require burned-in text. Check each platform's current upload options.

Course platforms and players: many accept SRT, though some prefer the closely related WebVTT format. Converting is usually a matter of changing the header and the comma in timestamps to a full stop; many tools do it automatically.

Burned-in vs closed captions: closed captions are a separate track viewers can switch on or off. Burned-in captions are part of the picture and always visible. Closed captions are generally more flexible; burned-in captions are common on short social videos.

Checklist for good captions

1. Write short sentences in the script so each caption is readable.
2. Download the SRT alongside your MP3 or WAV.
3. Watch the video with captions on and adjust any drift.
4. Split captions longer than two lines.
5. Check names, numbers and brand spellings.
6. Upload as closed captions where the platform supports it.

For a full production walkthrough, see how to make an AI voiceover for YouTube, or read more about what's included with every clip on the features page. You can try the free SRT subtitle generator now, or start free to get voiceover and subtitles together.