VoiceBox, Part of Wolfestone Group

Subtitles are the written representation of the audio in any form of moving picture, from a Hollywood blockbuster to a YouTube video on how to replace your spark plugs. They were originally used in the 1900s in the first cinematic films; the silent nature of these movies meant that filmmakers needed to add a little explanation of the action to keep the audience engaged. Once audio became possible in film and television, subtitles became a tool for accessibility, allowing those with hearing difficulties to understand the on-screen action. While this is still the primary function of subtitles, the explosion in the number of screens we use (as well as the amount of video content we now absorb) has seen subtitles become more frequently-used than ever, for a whole host of reasons. Indeed, a recent study by Ofcom suggests that 80% of subtitle users are not deaf.

If you are creating video content of any type, adding subtitles is certainly something to consider. It can boost the accessibility of your content, the attention your audience pays to it and even how much Google likes it. Read on to find out everything you need to know about adding subtitles to your video content.

Different types of subtitles

There are three main types of video subtitling services: open caption, closed caption and SDH (Subtitles for the Deaf and Hard of Hearing). The type you choose will depend on the purpose of your videos and your intended audience. We’ll expand more on this later, but first we’ll quickly define each type of subtitling.

Open caption subtitling

This is when the subtitles you create are permanently ‘burned in’ to your video, i.e. they can’t be turned off. In most cases, this is a decision you’ll make at the design stage of the filmmaking process, as you may need to leave space on screen for the words. (They aren’t always positioned at the bottom of the screen). This recent video by Forbes, regarding NASA’s renaming of its Washington HQ after Mary W. Jackson is a good example of this:


Closed caption subtitling

Typically offered as an option on DVDs, and more recently streaming services such as Netflix and BBC iPlayer, closed caption subtitles are the kind you’ll probably be most familiar with. These are the subtitles that can be turned on or off, and will almost always appear in one or two lines of text at the bottom of the screen.

SDH subtitles

These subtitles are similar to closed caption subtitling in that they are optional, and will usually appear at the bottom of the screen. The difference is that they have been created specifically with a deaf or hard of hearing audience in mind, and so will describe other audible details as well as the words, in order to help the audience understand the action or mood of the scene. For example, an SDH subtitle might read ‘sad music plays’, or ‘indistinct chatter’. This type of subtitling is most common on films, where action other than the words is important.

How is subtitling done?

The first step in the subtitling process is to transcribe the audio from the video. This simply means writing it out word for word. Once this document has been created, a subtitler will consider how best to use this text to create the most effective subtitles possible. Importantly, this isn’t always about copying the text word for word into subtitles. There are some fairly strict limitations with regards to character limit and the time a subtitle must remain on screen (more on these later), and so a subtitler’s role is often to represent the words in the most accurate way, while cutting it down to meet the restrictions. This requires a high degree of linguistic skill, and it is why we would always recommend working with a human subtitling agency over any subtitling software.

If the video is to be viewed in other languages, then the final stage is to translate the subtitles into these languages. Again, the benefits of the human touch at this stage cannot be overestimated; translation software might give a literal, word for word translation, but will miss the nuances such as humour, or the meaning of any idioms that might appear in the text. This ‘localisation’ of your subtitles that a skilled translator will add will enable your videos to really engage your overseas audiences.

Person using subtitles

Why use subtitles?

Whether the purpose of your video is to entertain, inform or sell your product (or indeed all three!) there are good reasons for adding captions. Four of the most common are:


The first, and perhaps most important reason for subtitling is still to make your content accessible for those who are deaf and hard of heading. Indeed, if you are making content for television you may well find subtitles are a legal requirement (Netflix were sued in 2011 for not providing adequate subtitling on their content). Around 5% of people have a hearing impairment of some kind, so you’ll be leaving out a fairly large section of your audience if you don’t provide subtitling.


SEO, or search engine optimisation is the name given to the process of helping your website or online content to achieve a high ranking in search engines. This is important, as studies have shown that over 50% of Internet traffic goes to the top three results.  Including video content on your website is a great way to boost your SEO, because Google views video content as more valuable than text.

Audiences agree: a survey by HubSpot found that 72% of customers would rather watch a video than read text on a screen. Adding subtitles to these videos will help boost your SEO even more. There are a few reasons for this. Firstly, the search engines tend to reward videos that have been watched all the way through with higher rankings. Including subtitles has been shown to double completion rates on videos, from 40% to 80%. Secondly, including a transcript gives the search engines more to read. Use a few well-placed key words within your subtitles and you’re helping Google, Bing and the like recognise you as a key player in your field.

Find out more about how transcripts and subtitles improve your SEO here.


We’ve already mentioned how much subtitles can help increase the number of people that watch your video all the way through, but it’s worth emphasising again: subtitling dramatically increases the engagement with your videos. This is especially true for social media videos. Why? One reason might be the shift in the way most of us consume video content these days: on our mobile devices. Very often, we’re ‘on the go’ when we watch these videos and the default setting is for the sound to be off. In fact, a recent study showed that over 80% of videos on Facebook are watched with the sound off. Fail to include subtitles, and unless your visuals are extremely clear, your message will only reach 20% of your audience. Need further proof? A study conducted by Facebook showed a 12% boost in view time for videos with subtitles.

International Reach

Of course, a major reason for subtitling is to deliver your message to an audience who don’t speak your language. It can be easy for English speakers to assume that the world, and the Internet all understand English. That couldn’t be further from the truth. In fact, less than 400 million people worldwide have English as their first language. Combine that with the fact that over 70% of customers say they would prefer to buy a product in their own language, then it becomes clear why subtitling translation is such an important marketing tool.

If you are looking to reach an international audience, then you may well need translation and subtitling services. Just as we wouldn’t recommend using auto-subtitling features, we would advise businesses to steer clear from the auto-translate plugins you can get such as srt translator, as they can miss the nuances of language. To really make sure your message gets across, you need subtitling and translation with localisation, which is the process of adapting language to make sure it fits the target culture.

People watching subtitled film.

Which type of subtitling does my content require?

While there are no hard and fast rules for this, generally speaking you will want to use open caption subtitling for social media videos, to make sure that the words are always seen. If your videos are intended for YouTube video, closed captioning is the better option, as users can turn them on and off as required, and you can include multilingual subtitle options on a single video.

If you know that your content is for an audience with hearing impairments, then you will need to follow guidelines for SDH subtitling.

If you are hosting a live event, you may require subtitles for live streaming. Find out more about our live caption services here.

Key considerations for subtitling

The final area we will focus on in this guide are some of the factors that must be considered when creating your subtitles. Even if you are not planning on writing your subtitles yourself, knowing these will help you understand why your subtitling company may recommend certain courses of action.

Line length

Subtitles are usually limited to 37 characters per line, and it’s advised to have no more than two lines of text on the screen at any one time. That leaves you with less characters to play with than a tweet (even on the old version of Twitter!). This means that subtitles may have to be more economical with the language that the audio on the video is. This is why we’d always recommend human video captioning services, as they will be able to cut down the word count without sacrificing any meaning.

Time on screen

It is good practice to give enough time for subtitles to be easily read, and a reading speed of 150 – 200 words per minute is recommended. That equates to about 3 seconds per line, which is usually slower than the dialogue or the script being captioned – another reason why you may need a skilled subtitler to make the language more succinct.


When it comes to spoken language, we’re often able to get our point across clearly without using grammatically correct sentences. Nothing wrong with this. But when it comes to written language, clarity comes from correct grammar and punctuation, so it’s good practice to make sure your subtitles contain these. This is another reason why it’s worth investing in a professional captioning service – they’ll know where all those pesky apostrophes are supposed to go!

In summary

We hope this guide has proved a useful introduction to subtitling, and has answered some of your questions around why your videos may need captions, as well as the process you might go through to achieve this.

At VoiceBox, we offer professional transcription, captioning and subtitling translation services in over 220 languages. If you’d like to find out more about how we could help your company add high quality subtitles to your video content, get in touch and speak to one of our team.