Words, timing and appearance
At minimum, a subtitle file holds words and times. Many formats can also hold instructions about how the words should look: where a cue sits on the screen, which color it uses, what font and size to prefer, whether it has a background, and how lines are aligned. Together these are often called caption styling. They are instructions, not guarantees. The player decides how much of the styling to honor.
Kinds of styling a file can carry
Position and alignment. A cue is normally placed at the bottom center. A file can move it to the top, to a side, or to a particular region of the frame, and set left, center or right alignment within that space. Moving a cue is common when it would otherwise cover on-screen text, a name caption or something important in the picture. Placement may also separate different speakers or sounds, a topic discussed in showing speaker changes in subtitles.
Color. Text color, and sometimes a separate color for the background box or outline, can be set. Color is sometimes used to tell speakers apart. That helps only when viewers can distinguish the colors, so it should not be the only signal, since some people have color vision differences. Always keep a name label or dash as a backup. The effect of hue on viewers is discussed in the article on subtitle color.
Fonts and size. Files may suggest a font family, a size, or a weight such as bold. Support varies widely, and a font named in a file has to be available on the viewer’s device. If it is missing, the player substitutes another. Sizes are often given relative to the frame or the default text size, not as an exact number of pixels, so results differ by screen.
Text effects. Italics, bold and underline are the most commonly supported. Italics are conventionally used for off-screen voices, thoughts or foreign words, covered in subtitle punctuation. Some formats also support outlines, shadows, and even motion, but these are rarer and less portable.
Backgrounds and outlines. A semi-opaque box or an outline can keep white text readable over bright scenes. This is a legibility feature more than a decorative one. The principles are covered under subtitle legibility.
Language and direction. Some formats can mark the language of a cue or the direction of the text. Right-to-left scripts in particular may depend on direction information to place punctuation correctly.
How different formats store styling
- The simplest text formats have no formal styling. Some players accept informal tags for italics or bold, but nothing is guaranteed, and other players may display the tags as literal text.
- Web-oriented formats allow cue settings for position and alignment, simple inline tags for things like italics and speaker voice, and style rules, similar to those used on web pages, that the page or file can supply. The page’s own rules can sometimes override those in the file.
- XML-based formats can define named styles and regions and apply them to cues, so a single style definition can be reused across a whole file. This makes them well suited to large projects with a consistent look.
- Advanced styling formats designed for desktop players allow detailed control, including fonts, outlines and animation, but are less widely supported in web or broadcast contexts.
- Image-based subtitles store the appearance as a picture, so there are no style fields to change; the look is fixed.
The overview of file formats compares these families in more detail.
Why styling does not always show up
The format does not support it. Converting a richly styled file into a plain-text format drops the styling. Nothing warns you, and the result may look fine until someone notices that the positions have gone.
The player ignores it. Some players apply their own defaults and disregard the file. Others honor only part of it, such as italics but not colors.
The viewer overrides it. Many devices let viewers set their own size, color, font and background, and these settings generally take priority over the file’s choices. This is intentional: it helps viewers who need larger or higher-contrast text. A good file therefore does not rely on its styling being obeyed. Viewers can explore these options in their device settings, and the article on subtitle appearance describes what they commonly find there.
The platform restricts it. Broadcast and streaming platforms often have their own style rules, and may strip or replace what a file specifies.
Good habits for styled files
- Use as little styling as the content needs. Plain, well-timed text in the default style is often the most reliable. Add position or color only for a clear reason.
- Do not rely on color alone. Pair it with labels or punctuation.
- Keep text clear of other on-screen text. If you move cues, test the placement at several screen sizes.
- Test in the target player. Styling that works in an editor may look different on a phone, a television or a browser.
- Keep an unstyled version of the text. It is a useful fallback if a platform rejects the styled one.
- Respect the rest of the rules. Styling does not change the need for sensible line length, line breaks and reading speed. Fancy formatting cannot rescue text that is too long to read.
- Document your choices. A short style note listing colors, positions and conventions helps others maintain consistency, and fits neatly into a style guidelines document.
A note on accessibility
Stored styling can help some viewers, for example by avoiding overlap with important visuals, but it can also work against them if it removes their control. The most accessible approach usually respects the viewer’s own settings. Accessibility expectations differ by place and sector; check with the relevant authority or a qualified professional if a requirement applies to you.