For the past 5 years, Ai-Media has been awarded a captioning quality score of over 99% by independent auditors. But how is a captioning quality score determined? What dictates good and bad quality captions? We're breaking down the basic guidelines that dictate how caption quality is measured and the importance of high-quality captions for media.

Types of errors

There are plenty of basic grammatical or formatting errors that can make captions harder to read. Anything from misspelling, punctuation, or speed of the text can impact someone’s ability to understand what is being said, and therefore will result in poor quality captions.


The most common forms of mistakes include:

  • There vs Their vs They're
  • You're vs Your
  • Lose vs Loose


Why does this happen? What affects the potential quality of captions? Well, there are a few reasons, including:

  • Difficulty of the language used
  • Multiple speakers
  • Number of natural pauses, and
  • Quality of the audio in the files provided


Caption Guidelines

Officially, many countries like Australia, the UK, and the United States, all have legislation, laws, and bodies that review and monitor the quality of captions that are allowed to be aired on screen. 

The Federal Communications Commission (FCC) in the United States has official regulations and rules surrounding captioning on television to ensure that viewers who are deaf and heard of hearing have full access. The infographic below outlines the FCC’s closed captioning standards which provide guidance to video programming distributors and programmers. 

5 Pannel graphic with text explaining Caption Quality Standards

Let's take a look at the specific elements that guide the standards of captions.


Reading Speed

Captions assist deaf and hard of hearing viewers access video content and understand what is being said. So, as a result, the speed at which the captions appear and how long they appear for are very important.


Typically, captions should not be so fast that they are difficult to read. Most companies which produce captions for TV and cinema adhere to minimum word speeds (typically 180-200 words per minute or about three words per second). If the dialogue is faster than this, then the language should be condensed, with unimportant words and repetitions eliminated (such as, "umm" and “ahh”).


Positioning and Colouring

Captions should be displayed at the bottom of the screen. However, captions will be raised to avoid obscuring any additional content on the screen including logos, subtitles, banners, news tickers or other visuals. Captions will rarely ever appear on the centre   of the screen as it may interfere with the visual storytelling. 


Small graphic showing figure speaking with captions

Captions for television are often coloured and positioned to help the viewer identify who is speaking. Media players depending on the type may not support or allow multi-coloured captions. In this instance, it is acceptable for captions to be all white and centred. In this scenario, the two speakers are differentiated by placing dashes before their respective lines, e.g.:


–   How are you?

–   I’m fine.


Additional ways of indicating speakers involve character names or descriptions, such as:


JOHN: Hello.


WOMAN: Hello.


Font Size

Captions must be written in a font which is large enough to be easily readable, taking into account the size of the screen. There are no accepted standards for this, but captions on Australian television are a maximum of 37 characters per line. 


Line Breaks

Line breaks should be made where there is a natural linguistic break in the sentence (e.g. after a comma). This helps audiences follow the natural rhythm and flow of a conversation, speech, or dialogue on screen easier. This also applies to longer sentences which go over multiple captions lines.


Below, we see how proper line breaks can improve of the same caption:

Line Breaks Incorrect and Correct Columns next to eachother


Web Content Accessibility Guidelines

Beyond the FCC and local legislation regarding quality, there is another set of guidelines that captioning services and businesses must meet. This is called the Web Content Accessibility Guidelines, or WCAG for short.


The Web Content Accessibility Guidelines (WCAG) is a series of web accessibility guidelines published by the Web Accessibility Initiative (WAI) of the World Wide Web Consortium (W3C). WCAG is the main international standards for the Internet and sets recommendations for accessible content aimed at people with disabilities. 


In 2008, WCAG 2.0 was published, providing 12 recommendations organized under 4 principals. These principals and recommendations are what captioning, and transcription services must adhere to when creating captions for online content.


These principals are:

Perceivable: Information and user interface components must be presentable to users in ways they can perceive.


Operable: User interface components and navigation must be operable.


Understandable: Information and the operation of user interface must be understandable.

Robust: Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies.


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