--- title: Web Video Text Tracks Format (WebVTT) slug: Web/API/WebVTT_API translation_of: Web/API/WebVTT_API ---

Web Video Text Tracks Format (WebVTT) est un format pour afficher du texte en fonction du temps (comme des sous-titres ou des légendes) en utilisant l'élément HTML {{HTMLElement("track")}}. L'objectif de ce format est d'afficher du texte sur {{HTMLElement("video")}}. WebVTT est un format texte codé en {{Glossary("UTF-8")}}. On peut utiliser aussi bien des espaces que des tabulations. Il y a aussi une petite API capable de représenter et de modifier ces pistes ainsi que les données nécéssaires à la synchornisation du texte.

Les fichiers WebVTT

Les fichiers WebVTT ont pour type MIME text/vtt.

Un fichier WebVTT (.vtt) contient les répliques qui peuvent être sur une ou plusieurs lignes.

WEBVTT

00:01.000 --> 00:04.000
Ne jamais boire de l'azote liquide.

00:05.000 --> 00:09.000
- Cela peut perforer l'estomac.
- On peut en mourir.

Le corps WebVTT

La structure d'un fichier WebVTT consiste en une série de composants, certains d'entre-eux sont optionnels. Dans l'ordre:

Indicateur d'ordre des octets {{optional_inline}}
La chaîne de caractères "WEBVTT".
Titre à droite de "WEBVTT". {{optional_inline}}
- Il doit y avoir au moins un espace après "WEBVTT".
- Vous pouvez l'utiliser pour mettre une description.
- Vous pouvez utiliser n'importe quoi à part une nouvelle ligne ou la chaîne "-->".
Une ligne vide équivalente à deux lignes consécutives.
Zéros ou plusieurs répliques ou commenatiaires.
Zéro ou plusieurs lignes vides.

Exemple 1 - Plus petit fichier WebVTT

WEBVTT

Exemple 2 - Simple fichier WebVTT contenant un entête

WEBVTT - Ce fichier ne possède pas de réplique.

Exemple 3 - Fichier WebVTT courant avec un entête et des répliques

WEBVTT - Ce fichier possède des répliques.

14
00:01:14.815 --> 00:01:18.114
- Quoi?
- Où sommes-nous?

15
00:01:18.171 --> 00:01:20.991
- C'est le pays des grandes chauves-souris.

16
00:01:21.058 --> 00:01:23.868
- [ Cris perçant de chauves-souris ]
- Elles ne veulent pas aller dans vos cheveux. Elles attrapent les insectes.

Structure interne d'un fichier WebVTT

Réexaminons le premier exemple, et observons la structure plus précisément.

WEBVTT

00:01.000 --> 00:04.000
Ne jamais boire de l'azote liquide.

00:05.000 --> 00:09.000
- Cela peut perforer l'estomac.
- On peut en mourir.

NOTE Cette ligne est la dernière ligne du fichier

Dans chaque réplique:

La première ligne commence par un temps correspondant au moment où il apparait.
Sur la même ligne nous avons une chaîne -->.
Nous finissions la ligne par un second temps indiquant la fin de l'affichage du texte.
Nous pouvons alors afficher une ou plusieurs lignes commençant par un tiret (-), chacune contenant une partie du texte à afficher.

Nous pouvons aussi mettre des commentaires dans notre fichier .vtt afin de nous aider à nous remémorer des informations importantes à propos du fichier. Ils doivent être séparés par une ligne vide et commencer par NOTE. Nous en reparlerons dans la prochaine section.

Il est important de ne pas utiliser de ligne vide sans réplique, par exemple entre la ligne indiquant le temps et le texte en lui même. WebVTT est basé sur les lignes, une ligne vide ferme la réplique.

Les commentaires WebVTT

Les commentaires sont des composants optionels qui peuvent être utilisés pour ajouter des informations à un fichier WebVTT. Les commentaires sont prévus pour ceux qui liront le fichier, ils ne seront pas vus par les utilisateurs. Les commentaires peuvent contenir de nouvelles ligne mais ne peuvent pas contenir de ligne vide ce qui équivaut à deux nouvelles lignes. Une ligne vide correspond à la fin d'un commentaire.

Un commentaire ne peut contenir la chaîne "-->", l'esperluette & ou bien le symbole plus-petit que <. Si vous voulez utiliser ces caractères, vous devez utiliser les caractères échapés comme &pour l'esperluette et < pour le plus petit que. Il est aussi recommandé > pour le plus grand que, afin d'éviter toutes confusions.

Un commentaire est constitué de ces trois composants:

La chaîne NOTE.
Un espace ou une nouvelle ligne.
Aucun ou plusieurs caractères sauf ceux indiqué ci-dessus.

Exemple 4 - Simple commentaire WebVTT

NOTE Ceci est un simple commentaire

Exemple 5 - Multi-line comment

NOTE
Un autre commentaire qui est
coupé sur plusieurs lignes.

NOTE Vous pouvez aussi faire un commentaire
sur plusieurs lignes de cette façon.

Exemple 6 - Usage commun des commentaires

WEBVTT - Traduction de ce film que j'aime

NOTE
Cette traduction a été faite par Kyle pour que
ses amis puissent la voir avec leurs parents.

1
00:02:15.000 --> 00:02:20.000
- Ta en kopp varmt te.
- Det är inte varmt.

2
00:02:20.000 --> 00:02:25.000
- Har en kopp te.
- Det smakar som te.

NOTE Cette dernière ligne n'est pas forcément bien traduite.

3
00:02:25.000 --> 00:02:30.000
- Ta en kopp

Styliser les répliques WebTT

Vous pouvez styliser des répliques WebVTT en cherchant les éléments qui correspondent à la pseudo-classe {{cssxref("::cue")}}.

Avec du CSS

video::cue {
  background-image: linear-gradient(to bottom, dimgray, lightgray);
  color: papayawhip;
}

video::cue(b) {
  color: peachpuff;
}

Here, all video elements are styled to use a gray linear gradient as their backgrounds, with a foreground color of "papayawhip". In addition, text boldfaced using the {{HTMLElement("b")}} element are colored "peachpuff".

The HTML snippet below actually handles displaying the media itself.

<video controls autoplay src="video.webm">
 <track default src="track.vtt">
</video>

Dans le fichier WebVTT

You can also define the style directly in the WebVTT file. In this case, you insert your CSS rules into the file with each rule preceded by the string "STYLE" all by itelf on a line of text, as shown below:

WEBVTT

STYLE
::cue {
  background-image: linear-gradient(to bottom, dimgray, lightgray);
  color: papayawhip;
}
/* Style blocks cannot use blank lines nor "dash dash greater than" */

NOTE comment blocks can be used between style blocks.

STYLE
::cue(b) {
  color: peachpuff;
}

00:00:00.000 --> 00:00:10.000
- Hello <b>world</b>.

NOTE style blocks cannot appear after the first cue.

We can also use identifiers inside WebVTT file, which can be used for defining a new style for some particular cues in the file. The example where we wanted the transcription text to be red highlighted and the other part to remain normal, we can define it as follows using CSS. Where it must be noted that the CSS uses escape sequences the way they are used in HTML pages:

WEBVTT

1
00:00.000 --> 00:02.000
That’s an, an, that’s an L!

crédit de transcription
00:04.000 --> 00:05.000
Transcrit par Célestes™

::cue(#\31) { color: lime; }
::cue(#crédit\ de\ transcription) { color: red; }

Positioning of text tracks is also supported, by including positioning information after the timings in a cue, as seen below (see {{anch("Cue settings")}} for more information):

WEBVTT

00:00:00.000 --> 00:00:04.000 position:10%,line-left align:left size:35%
Where did he go?

00:00:03.000 --> 00:00:06.500 position:90% align:right size:35%
I think he went down this lane.

00:00:04.000 --> 00:00:06.500 position:45%,line-right align:center size:35%
What are you waiting for?

Les répliques WebVTT

A cue is a single subtitle block that has a single start time, end time, and textual payload. Example 6 consists of the header, a blank line, and then five cues separated by blank lines. A cue consists of five components:

An optional cue identifier followed by a newline.
Cue timings.
Optional cue settings with at least one space before the first and between each setting.
One or more newlines.
The cue payload text.

Exemple 7 - Exemple de réplique

1 - Title Crawl
00:00:05.000 --> 00:00:10.000 line:0 position:20% size:60% align:start
Some time ago in a place rather distant....

Cue identifier

The identifier is a name that identifies the cue. It can be used to reference the cue from a script. It must not contain a newline and cannot contain the string "-->". It must end with a single newline. They do not have to be unique, although it is common to number them (e.g., 1, 2, 3, ...).

Example 8 - Cue identifier from Example 7

1 - Title Crawl

Example 9 - Common usage of identifiers

WEBVTT

1
00:00:22.230 --> 00:00:24.606
This is the first subtitle.

2
00:00:30.739 --> 00:00:34.074
This is the second.

3
00:00:34.159 --> 00:00:35.743
Third

Cue timings

A cue timing indicates when the cue is shown. It has a start and end time which are represented by timestamps. The end time must be greater than the start time, and the start time must be greater than or equal to all previous start times. Cues may have overlapping timings.

If the WebVTT file is being used for chapters ({{HTMLElement("track")}} {{htmlattrxref("kind")}} is chapters) then the file cannot have overlapping timings.

Each cue timing contains five components:

Timestamp for start time.
At least one space.
The string "-->".
At least one space.
Timestamp for end time.
- Which must be greater than the start time.

The timestamps must be in one of two formats:

mm:ss.ttt
hh:mm:ss.ttt

Where the components are defined as follows:

hh is hours.
- Must be at least two digits.
- Hours can be greater than two digits (e.g., 9999:00:00.000).
mm is minutes.
- Must be between 00 and 59 inclusive.
ss is seconds.
- Must be between 00 and 59 inclusive.
ttt is miliseconds.
- Must be between 000 and 999 inclusive.

Example 10 - Basic cue timing examples

00:22.230 --> 00:24.606
00:30.739 --> 00:00:34.074
00:00:34.159 --> 00:35.743
00:00:35.827 --> 00:00:40.122

Example 11 - Overlapping cue timing examples

00:00:00.000 --> 00:00:10.000
00:00:05.000 --> 00:01:00.000
00:00:30.000 --> 00:00:50.000

Example 12 - Non-overlapping cue timing examples

00:00:00.000 --> 00:00:10.000
00:00:10.000 --> 00:01:00.581
00:01:00.581 --> 00:02:00.100
00:02:01.000 --> 00:02:01.000

Cue settings

Cue settings are optional components used to position where the cue payload text will be displayed over the video. This includes whether the text is displayed horizontally or vertically. There can be zero or more of them, and they can be used in any order so long as each setting is used no more than once.

The cue settings are added to the right of the cue timings. There must be one or more spaces between the cue timing and the first setting and between each setting. A setting's name and value are separated by a colon. The settings are case sensitive so use lower case as shown. There are five cue settings:

vertical
- Indicates that the text will be displayed vertically rather than horizontally, such as in some Asian languages.
Table 1 - vertical values

vertical:rl writing direction is right to left

vertical:lr writing direction is left to right

Table 1 - vertical values
`vertical:rl`	writing direction is right to left
`vertical:lr`	writing direction is left to right

line

Specifies where text appears vertically. If vertical is set, line specifies where text appears horizontally.
Value can be a line number.
- The line height is the height of the first line of the cue as it appears on the video.
- Positive numbers indicate top down.
- Negative numbers indicate bottom up.
Or value can be a percentage.
- Must be an integer (i.e., no decimals) between 0 and 100 inclusive.
- Must be followed by a percent sign (%).

Table 2 - line examples
	`vertical` omitted	`vertical:rl`	`vertical:lr`
`line:0`	top	right	left
`line:-1`	bottom	left	right
`line:0%`	top	right	left
`line:100%`	bottom	left	right

position

Specifies where the text will appear horizontally. If vertical is set, position specifies where the text will appear vertically.
Value is a percentage.
Must be an integer (no decimals) between 0 and 100 inclusive.
Must be followed by a percent sign (%).

Table 3 - position examples
	`vertical` omitted	`vertical:rl`	`vertical:lr`
`position:0%`	left	top	top
`position:100%`	right	bottom	bottom

size

Specifies the width of the text area. If vertical is set, size specifies the height of the text area.
Value is a percentage.
Must be an integer (i.e., no decimals) between 0 and 100 inclusive.
Must be followed by a percent sign (%).

Table 4 - size examples
	`vertical` omitted	`vertical:rl`	`vertical:lr`
`size:100%`	full width	full height	full height
`size:50%`	half width	half height	half height

align

Specifies the alignment of the text. Text is aligned within the space given by the size cue setting if it is set.

Table 5 - align values
	`vertical` omitted	`vertical:rl`	`vertical:lr`
`align:start`	left	top	top
`align:middle`	centred horizontally	centred vertically	centred vertically
`align:end`	right	bottom	bottom

Example 13 - Cue setting examples

The first line demonstrates no settings. The second line might be used to overlay text on a sign or label. The third line might be used for a title. The last line might be used for an Asian language.

00:00:05.000 --> 00:00:10.000
00:00:05.000 --> 00:00:10.000 line:63% position:72% align:start
00:00:05.000 --> 00:00:10.000 line:0 position:20% size:60% align:start
00:00:05.000 --> 00:00:10.000 vertical:rt line:-1 align:end

Cue payload

The payload is where the main information or content is located. In normal usage the payload contains the subtitles to be displayed. The payload text may contain newlines but it cannot contain a blank line, which is equivalent to two consecutive newlines. A blank line signifies the end of a cue.

A cue text payload cannot contain the string "-->", the ampersand character (&), or the less-than sign (<). Instead use the escape sequence "&" for ampersand and "<" for less-than. It is also recommended that you use the greater-than escape sequence ">" instead of the greater-than character (>) to avoid confusion with tags. If you are using the WebVTT file for metadata these restrictions do not apply.

In addition to the three escape sequences mentioned above, there are fours others. They are listed in the table below.

Table 6 - Escape sequences
Name	Character	Escape Sequence
Ampersand	&	`&`
Less-than	<	`<`
Greater-than	>	`>`
Left-to-right mark		`&lrm;`
Right-to-left mark		`&rlm;`
Non-breaking space		` `

Cue payload text tags

There are a number of tags, such as <bold>, that can be used. However, if the WebVTT file is used in a {{HTMLElement("track")}} element where the attribute {{htmlattrxref("kind")}} is chapters then you cannot use tags.

Timestamp tag
- The timestamp must be greater that the cue's start timestamp, greater than any previous timestamp in the cue payload, and less than the cue's end timestamp. The active text is the text between the timestamp and the next timestamp or to the end of the payload if there is not another timestamp in the payload. Any text before the active text in the payload is previous text . Any text beyond the active text is future text . This enables karaoke style captions.
Example 12 - Karaoke style text
```
1
00:16.500 --> 00:18.500
When the moon <00:17.500>hits your eye

1
00:00:18.500 --> 00:00:20.500
Like a <00:19.000>big-a <00:19.500>pizza <00:20.000>pie

1
00:00:20.500 --> 00:00:21.500
That's <00:00:21.000>amore
```

The following tags are the HTML tags allowed in a cue and require opening and closing tags (e.g., text).

Class tag (<c></c>)
- Style the contained text using a CSS class.
Example 14 - Class tag
```
<c.classname>text</c>
```
Italics tag ()
- Italicize the contained text.
Example 15 - Italics tag
```
text
```
Bold tag ()
- Bold the contained text.
Example 16 - Bold tag
```
text
```
Underline tag ()
- Underline the contained text.
Example 17 - Underline tag
```
text
```
Ruby tag (<ruby></ruby>)
- Used with ruby text tags to display ruby characters (i.e., small annotative characters above other characters).
Example 18 - Ruby tag
```
<ruby>WWW<rt>World Wide Web</rt>oui<rt>yes</rt></ruby>
```
Ruby text tag (<rt></rt>)
- Used with ruby tags to display ruby characters (i.e., small annotative characters above other characters).
Example 19 - Ruby text tag
```
<ruby>WWW<rt>World Wide Web</rt>oui<rt>yes</rt></ruby>
```
Voice tag (<v></v>)
- Similar to class tag, also used to style the contained text using CSS.
Example 20 - Voice tag
```
<v Bob>text</v>
```

Interfaces

There are two interfaces or APIs used in WebVTT which are:

VTTCue interface

It is used for providing an interface in Document Object Model API, where different attributes supported by it can be used to prepare and alter the cues in number of ways.

Constructor is the first point for starting the Cue which is defined using the default constructor VTTCue(startTime, endTime, text) where starting time, ending time and text for cue can be adjusted. After that we can set the region for that particular cue to which this cue belongs using cue.region. Vertical, horizontal, line, lineAlign, Position, positionAlign, text, size and Align can be used to alter the cue and its formation, just like we can alter the objects form, shape and visibility in HTML using CSS. But the VTTCue interface is within the WebVTT provides the vast range of adjustment variables which can be used directly to alter the Cue. Following interface can be used to expose WebVTT cues in DOM API:

enum AutoKeyword { "auto" };
enum DirectionSetting { "" /* horizontal */, "rl", "lr" };
enum LineAlignSetting { "start", "center", "end" };
enum PositionAlignSetting { "line-left", "center", "line-right", "auto" };
enum AlignSetting { "start", "center", "end", "left", "right" };
[Constructor(double startTime, double endTime, DOMString text)]
interface VTTCue : TextTrackCue {
  attribute VTTRegion? region;
  attribute DirectionSetting vertical;
  attribute boolean snapToLines;
  attribute (double or AutoKeyword) line;
  attribute LineAlignSetting lineAlign;
  attribute (double or AutoKeyword) position;
  attribute PositionAlignSetting positionAlign;
  attribute double size;
  attribute AlignSetting align;
  attribute DOMString text;
  DocumentFragment getCueAsHTML();
};

VTTRegion interface

This is the second interface in WebVTT API.

The new keyword can be used for defining a new VTTRegion object which can then be used for containing the multiple cues. There are several properties of VTTRegion which are width, lines, regionAnchorX, RegionAnchorY, viewportAnchorX, viewportAnchorY and scroll that can be used to specify the look and feel of this VTT region. The interface code is given below which can be used to expose the WebVTT regions in DOM API:

enum ScrollSetting { "" /* none */, "up" };
[Constructor]
interface VTTRegion {
  attribute double width;
  attribute long lines;
  attribute double regionAnchorX;
  attribute double regionAnchorY;
  attribute double viewportAnchorX;
  attribute double viewportAnchorY;
  attribute ScrollSetting scroll;
};

Methods and properties

The methods used in WebVTT are those which are used to alter the cue or region as the attributes for both interfaces are different. We can categorize them for better understanding relating to each interface in WebVTT:

VTTCue
- The methods which are available in this interface are:
  - GetCueAsHTML to get the HTML of that Cue.
  - VTT Constructor for creating new objects of Cues.
  - Autokeyword.
  - DirectionSetting: to set the direction of caption or text in a file.
  - LineAlignment: to adjust the line alignment.
  - PositionAlignSetting: to adjust the position of text.
VTTRegion
- The methods used for region are listed below along with description of their functionality:
  - ScrollSetting: For adjusting the scrolling setting of all nodes present in given region.
  - VTT Region Constructor: for construction of new VTT Regions.

Tutorial on how to write a WebVTT file

There are few steps that can be followed to write a simple webVTT file. Before start, it must be noted that you can make use of a notepad and then save the file as ‘.vtt’ file. Steps are given below:

Open a notepad.
The first line of WebVTT is standardized similar in the way some other languages require you to put headers as the file starts to indicate the file type. One the very first line you have to write.

WEBVTT

3. Leave the second line blank, and on the third line the time for first cue is to be specified. For example, for a first cue starting at time 1 second and ending at 5 seconds, it is written as:

00:01.000 --> 00:05.000

On the next line you can write the caption for this cue which will run from 1^st second to the 5^th second, inclusive.
Following the similar steps, a complete WebVTT file for specific video or audio file can be made.

CSS pseudo-classes

CSS pseudo classes allow us to classify the type of object which we want to differentiate from other types of objects. It works in similar manner in WebVTT files as it works in HTML file.

It is one of the good features supported by WebVTT is the localization and use of class elements which can be used in same way they are used in HTML and CSS to classify the style for particular type of objects, but here these are used for styling and classifying the Cues as shown below:

WEBVTT

04:02.500 --> 04:05.000
J’ai commencé le basket à l'âge de 13, 14 ans

04:05.001 --> 04:07.800
Sur les <i.foreignphrase><lang en>playground</lang></i>, ici à Montpellier

In the above example it can be observed that we can use the identifier and pseudo class name for defining the language of caption, where  tag is for italics.

The type of pseudo class is determined by the selector it is using and working is similar in nature as it works in HTML. Following CSS pseudo classes can be used:

Lang (Lanugage): e.g., p:lang(it).
Link: e.g., a:link.
Nth-last-child: e.g., p:nth-last-child(2).
Nth-child(n): e.g., p:nth-child(2).

Where p and a are the tags which are used in HTML for paragraph and link, respectively and they can be replaced by identifiers which are used for Cues in WebVTT file.

Spécifications

Specification	Status	Comment
{{SpecName("WebVTT")}}	{{Spec2("WebVTT")}}	Définition initiales

Compatibilité des navigateurs

`VTTCue` interface

`TextTrack` interface

Notes

Prior to Firefox 50, the AlignSetting enum (representing possible values for {{domxref("VTTCue.align")}}) incorrectly included the value "middle" instead of "center". This has been corrected.

WebVTT was implemented in Firefox 24 behind the preference {{pref("media.webvtt.enabled")}}, which is disabled by default; you can enable it by setting this preference to true. WebVTT is enabled by default starting in Firefox 31 and can be disabled by setting the preference to false.

Prior to Firefox 58, the REGION keyword was creating {{domxref("VTTRegion")}} objects, but they were not being used. Firefox 58 now fully supports VTTRegion and its use; however, this feature is disabled by default behind the preference media.webvtt.regions.enabled; set it to true to enable region support in Firefox 58. Regions are enabled by default starting in Firefox 59 (see bugs {{bug(1338030)}} and {{bug(1415805)}}).

Les fichiers WebVTT

Le corps WebVTT

Exemple 1 - Plus petit fichier WebVTT

Exemple 2 - Simple fichier WebVTT contenant un entête

Exemple 3 - Fichier WebVTT courant avec un entête et des répliques

Structure interne d'un fichier WebVTT

Les commentaires WebVTT

Exemple 4 - Simple commentaire WebVTT

Exemple 5 - Multi-line comment

Exemple 6 - Usage commun des commentaires

Styliser les répliques WebTT

Avec du CSS

Dans le fichier WebVTT

Les répliques WebVTT

Exemple 7 - Exemple de réplique

Cue identifier

Example 8 - Cue identifier from Example 7

Example 9 - Common usage of identifiers

Cue timings

Example 10 - Basic cue timing examples

Example 11 - Overlapping cue timing examples

Example 12 - Non-overlapping cue timing examples

Cue settings

Example 13 - Cue setting examples

Cue payload

Cue payload text tags

Example 12 - Karaoke style text

Example 14 - Class tag

Example 15 - Italics tag

Example 16 - Bold tag

Example 17 - Underline tag

Example 18 - Ruby tag

Example 19 - Ruby text tag

Example 20 - Voice tag

Interfaces

VTTCue interface

VTTRegion interface

Methods and properties

VTTCue

VTTRegion

Tutorial on how to write a WebVTT file

CSS pseudo-classes

Spécifications

Compatibilité des navigateurs

VTTCue interface

TextTrack interface

Notes

`VTTCue` interface

`TextTrack` interface