What are SRT files?

A file with the .SRT extension is one of the most commonly-used captioning file formats. They contain the text of what's being said in the video along with the timing for those words and the order in which they appear.

Interested in learning more about captions? Check out our Complete Guide to Closed Captioning.

The SRT file type was developed in Europe, its name and format stemming from SubRip software, used for ‘ripping’ or extracting subtitles from films and exporting that information as an SRT.  

The format contains only the subtitle information, working together with the video for the final product. Think of the SRT as complimentary to your video file, rather than as its replacement. When an SRT file is loaded to a compatible video platform, captions will be displayed in the foreground of the media, as per the information contained in that file.

Although more sophisticated formats exist, including those allowing the user to specify the style or positioning of captions, SRT files serve as the most widely used and supported of all.

The simplicity of the format becomes obvious from this deconstruction of one caption block:

00:00:23,920 --> 00:00:28,560
That's the same weight
as around 450 adult elephants.


The first line, containing a single number (in this example 6), is the caption block number. These numbers give the order of the caption blocks, so the caption before this one would have number 5 as its block number, the following caption would have 7, and so on.


The next line down specifies the times at which the caption appears and disappears, known as timecodes. These timecodes correspond to the appropriate times in the video when the caption should be displayed.

Timecodes are given in the format hours : minutes : seconds , milliseconds. So, in this example, the caption would appear on screen 23 seconds and 920 milliseconds into the video, then disappear at 28 seconds and 560 milliseconds in.


Below the timecodes are the most important part of the block - the actual words of the caption. Each caption block tends to be one or two lines, with a 32-character limit on each line, arranged so they’re as readable as possible for the viewer. And - believe it or not - there’s a semi-science as to how this arrangement should be done!

Finally, the end of the caption is then denoted by an empty line which separates one block from the next.


Why use SRT files?

1. Ease of use

Since they are both easy to create and update, SRT files are a hassle-free way to add captions to video.  Given they are simply a text file, there is no requirement for specialised software. Instead, they are editable in any basic text editor, usually already installed and ready to go on your computer, such as Notepad or TextEdit. To edit, simply make your change(s), save and re-upload!

Additionally, being such a widely used format, SRTs are compatible with virtually all platforms and players, including Facebook, YouTube, Windows Media Player and many more. What’s more here – one single file can be used across multiple platforms. The SRT has multi-modal capabilities, with no need for fiddly editing or to generate any additional files.   

2. Audience engagement

There is no denying that captions increase viewer engagement with video content:

  • 85% of all Facebook videos are watched without sound (Digiday)
  • Average shares on Facebook drop by around 15% when captions are removed
  • CTA (call to action) clicks fall by 26% when captions are removed
  • 10-second video views are 18% lower without captions

There is no good reason to not caption your video. You'll reach viewers faster, keep them engaged longer, and provide greater access to deaf and hard of hearing audiences. And what’s more, this can all be achieved through an incredibly simple step.

Best of all, it works in any context. Captions help students retain content and take better notes, it improves literacy and reading skills and allows students to remain more engaged with the content.

3. SEO

Search Engine Optimisation, or simply SEO, refers to the process of increasing a website’s visibility and ranking in the online sphere. In the digital age, this is integral. Captions are a simple way to reap SEO benefits when it comes to videos, as the automated bots that scan and index web pages do not readily process video data. The SRT offers a written version of the video, making it crawlable to search engines. That means additional context and keywords to help viewers find their way to your video. 

While closed captions (and transcripts) are rich in keywords, there is much more to it than that. Gone are the days of keyword stuffing! User Experience (UX) is increasingly playing a factor as a ranking factor. For example, search engines such as Google and YouTube now utilise watch time over view counts. What does this mean? More emphasis on audience engagement and accessibility, which as discussed above, closed captioning offers.

With closed captioning a ranking factor for major search engines like YouTube, it’s worth keeping in mind for future uploads, or even trawling through previous videos and adding captions to maximise your SEO benefits. Notably too, search engines will often have filter options allowing a user to include only videos with closed captions. Therefore, a failure to include captions here means an instant minimisation of your potential audience. 

It’s worth noting, YouTube’s auto-captions (ASR) aren’t useful for SEO purposes due to their inaccuracies, and won’t be indexed. Nor will open captions provide the wanted boost either, as they are embedded into the video and inaccessible to bots. SRT files are a simple way to add closed captions and optimise your videos. Another benefit? Your SRT doubles as a transcript of your video content, which can be repurposed for future content creation.


How do you make an SRT files?

There are loads of options for creating an SRT file. You could use captioning software that allows you to save your file as an SRT. Check out this article for the best free captioning tools.

SRT files are simple enough that they can be produced in Notepad (if you’re using Windows) or TextEdit (if you’re using a Mac). Ultimately, however, you can create an SRT using virtually any text editor. To create your own SRT file for a video you’d like to subtitle, you’ll need to have the content of your captions and the relevant timecodes at hand.

1. Open TextEdit. In our text editor, we’ll start off with building our very first caption block, numbered 1. Keeping in mind the timecode format (hours : minutes : seconds , milliseconds) and remembering to separate timecodes with an arrow, we can make a block:

2. To build our second block, we need to remember to add an empty line between our blocks. Otherwise, we can build it in a similar way to the first block:

3. We can continue this process with sequentially numbered blocks until all the captions are complete.

4. Once we’re ready to save the completed SRT file, we can do so via the File -> Save menu, remembering to save as type *.srt:

If you’re on a Mac, this will look a little bit different. You’ll need to uncheck the ‘Hide extension’ and ‘If no extension is provided’ checkboxes.

It’s easy enough to type out all the words that are said in your video, but some captions are definitely easier to read than others. To create the best SRT, it's worth considering the readability of your captions for your viewers. Here's a few handy hints: 

  • Break your captions at natural language breaks 
  • Break your captions up relatively evenly 
  • Don't go over two lines of text
  • Spell check, spell check, spell check! 

And the golden rule: 

  • Give people enough time to read your captions 

How to open an SRT file 

As previously mentioned, being a simple text file, any text editor can be used to open SRT files. While this is handy for editing purposes, the bigger question is how to open it alongside your video. 

Let’s take a common video player as an example – VLC media player. Once you’ve opened your desired clip, click the ‘Video’ drop down, followed by ‘Open Subtitle File’ and select the appropriate .srt. Your captions will now play alongside your video. Other video players follow a similar protocol. 

How to upload an SRT file for Facebook

Uploading your SRT to a hosted video player, such as Facebook, YouTube, Vimeo etc, is a little bit different, but still very simple! 

When uploading your video to Facebook, toggle to the ‘Captions’ tab. From here, click 'Upload SRT file' and select the .srt from your computer. It’s important to note, you'll need to make sure your naming convention is correct before you upload. For English closed captions, the name should be 'filename.en_US.srt'. 

For a full step-by-step, we’ve created a complete walkthrough on how to add closed captions to Facebook

So, you now have all the tools needed to create and publish your own closed captions using the SRT format. As outlined, the SRT is a widely used and compatible format, allowing you complete control of your captions, with numerous benefits for your audience and your business. 


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