What Is SDH? — Subtitles for the Deaf and Hard of Hearing

SDH stands for Subtitles for the Deaf and Hard of Hearing. The term was introduced by the DVD industry and is now widely used by streaming platforms.

You'll see SDH labeled in different ways depending on the platform:

• Netflix: an SDH badge on the title page; in the subtitle menu, tracks such as "English [CC]".
• Disney+: caption tracks are marked in the subtitle list; the exact label can vary by title.
• Amazon Prime Video: labels vary by title and device; look for CC or SDH next to the language.
• Apple TV: a CC or SDH badge on titles that have these tracks.
• HBO Max: caption tracks tagged CC, such as "English - CC".

The naming inconsistency is annoying but they all mean the same thing: subtitles that include sound effects and speaker IDs for deaf or hard-of-hearing viewers, in the language indicated.

Four common video text/audio options exist. SDH sits in the middle of the matrix.

The shorthand: subtitles handle language. Closed captions handle accessibility. SDH puts caption-level detail into a subtitle track, in the audio language or a translation. Dubbing replaces the audio entirely.

For a deeper comparison of subtitles vs captions, see closed captions vs subtitles. For dubbing vs subtitles see what is dubbing.

To make the differences concrete: imagine a Spanish film scene where a door slams, ominous music plays, and a character named Sofia says "I never should have come back here" in Spanish.

Original audio

Door slams. Music plays. Sofia (in Spanish): "Nunca debería haber regresado aquí."

Spanish subtitles (for someone watching the original who reads Spanish)

Nunca debería haber regresado aquí.

English subtitles (for hearing English speakers watching Spanish original)

I never should have come back here.

Spanish closed captions (for deaf Spanish speakers)

[puerta cerrándose de golpe]
[música siniestra]
SOFIA: Nunca debería haber regresado aquí.

English SDH (for deaf English speakers)

[door slams]
[ominous music]
SOFIA: I never should have come back here.

Notice the SDH track has both the language translation (Spanish → English) AND the sound effects + speaker IDs that closed captions include. It is the most complete information a viewer can have without hearing the audio.

Most major streaming platforms offer SDH or CC tracks on many titles, but the toggle location varies. The audio/subtitle picker is usually accessed via a speech-bubble icon while playing.

Netflix

1. Start playing a title.
2. Click the speech-bubble icon (Audio & Subtitles).
3. Look for tracks tagged "[CC]" or "[SDH]" — for example "English [CC]".
4. Select your preferred language.

Not all titles have SDH, and some shows lack it for some seasons or episodes. Titles that have it show an SDH badge on their details page.

Disney+

1. Click the audio/subtitles icon during playback.
2. Look for a track marked as captions (the label can vary by title).
3. Select the version you want.

Amazon Prime Video

1. Click the speech-bubble icon during playback.
2. Choose from the Subtitles list — caption-style tracks may be tagged CC or SDH; labels vary by title and device.

Apple TV / iTunes

1. During playback, open the subtitles control and choose a track tagged SDH or CC.
2. To always prefer these tracks, go to Settings → Accessibility → Subtitles and Captioning and turn on Closed Captions and SDH.

HBO Max / Max

1. Click the speech-bubble (Audio and Subtitles) icon during playback.
2. Under Subtitles, caption tracks are tagged CC — for example "English - CC".

Hulu

1. Click the gear (Settings) icon during playback.
2. Open the subtitles options and pick a language.

Customising SDH appearance

Most platforms let you change SDH font size, color, background, and edge style for readability. Look for "Subtitle Appearance" or "Caption Style" in the platform's account settings (not just per-video).

Closed captions and SDH overlap heavily. Both include sound effects and speaker IDs. Why are they different formats?

Historical reasons

Closed captions were invented for U.S. broadcast TV in the 1970s and standardised as CEA-608 (later CEA-708) — formats designed for over-the-air broadcast. They are technically tied to the broadcast video signal. SDH came later: the term was introduced by the DVD industry for subtitle-style tracks on home video rather than captions carried in the broadcast signal.

Technical reasons

Classic broadcast captions are drawn by the TV's own decoder, usually as white text on a black band, and are carried in the video signal (line 21, or as data in digital TV). SDH is carried as a regular subtitle track (a subtitle stream on DVD, or files like SRT, VTT or TTML for streaming), so it usually looks like normal subtitles.

Editorial reasons

U.S. closed captions often place text near the person speaking and mark music with a note symbol (♪). SDH usually follows the subtitle style of each distributor — often the same font as regular subtitles, with text centered. Netflix, for example, publishes its own timed-text style guides.

In practice today

For streaming platforms, the technical distinction between CC and SDH is mostly historical. Both are usually delivered as text tracks in modern formats. Platforms use the two labels loosely, so check what a track contains rather than what it is called.

If you're creating video for distribution and choosing what text tracks to include:

• Single-market, hearing audience: Skip subtitles entirely if the audience speaks the audio language. Add closed captions only for accessibility compliance.
• Single-market, mixed accessibility audience: Closed captions in the source language. SDH adds nothing here.
• Multi-language hearing audience: Subtitles in each target language. SDH not needed.
• Multi-language with accessibility: Subtitles + SDH per language.
• U.S. broadcast TV: Closed captions (CEA-608/708). FCC mandates them.
• Cinema (theatrical release): Open captions for accessibility screenings. Subtitle DCPs for international cinemas.

Cost implications

SDH costs more to produce than regular subtitles because the editor has to add sound effect descriptions and speaker IDs. Prices vary by vendor, language and turnaround, but the order is usually:

• AI-generated captions / SDH with human review: lowest cost
• Human-produced subtitles: higher
• Human-produced SDH: higher again, because there is more to write
• Human translation + SDH for a foreign language: highest

Each extra language adds its own cost, so smaller producers often limit SDH to the main language.

SDH uses standard subtitle file formats with editorial conventions for the SDH-specific elements. The file format itself is the same as regular subtitles.

File formats

• SRT — Widely supported; many platforms accept it. SRT reference.
• VTT (WebVTT) — Standard for HTML5 web video. VTT reference.
• TTML / DFXP — XML-based, used by Netflix and major streaming platforms for richer styling.
• iTT — Apple's iTunes Timed Text format for Apple TV / iTunes submissions.

SDH conventions inside the file

• Speaker IDs in caps with colon: SARAH: "Hello." Or in some conventions [SARAH]: "Hello."
• Sound effects in square brackets: [door slams], [ominous music], [audience laughs].
• Music descriptions: [melancholy piano music], [upbeat song begins], or with a music note: ♪ Song title ♪
• Off-screen sounds: [phone rings off-screen], [gunshot in distance].
• Mood indicators: [whispering], [shouting], [crying] when not visually clear.
• Foreign language preservation: SARAH: [in Spanish] Estoy bien. Or italics for foreign-language portions.
• Inaudible markings: [inaudible] when speech can't be transcribed.

Example SRT with SDH conventions

1
00:00:01,000 --> 00:00:03,000
[door creaks open]

2
00:00:03,500 --> 00:00:06,500
[ominous piano music begins]

3
00:00:07,000 --> 00:00:11,000
SARAH: I never should have come back here.

4
00:00:11,500 --> 00:00:14,000
[in Spanish] Mi madre.

Accessibility regulations around the world treat SDH similarly to closed captions:

• U.S. — FCC, Section 508, ADA: The FCC requires captions on most TV programming, Section 508 requires them on federal agency video, and some courts have applied the ADA to online video. These rules ask for captions; they do not name SDH.
• U.S. — CVAA (Twenty-First Century Communications and Video Accessibility Act): Online video that originally aired on TV with captions must include captions when redistributed online.
• EU — European Accessibility Act (EAA, in force since 28 June 2025): Services that give access to TV and streaming must pass on subtitles and other access services and let users control how they are shown.
• UK — Equality Act 2010: Requires reasonable adjustments for disabled people, which can include captions on video.
• Canada — Accessible Canada Act: Federal-level accessibility requirements; in Ontario, the AODA requires many organisations' websites to meet WCAG 2.0 Level AA, which includes captions for pre-recorded video.
• Australia — Disability Discrimination Act + Broadcasting Services Act: Captioning rules for free-to-air broadcast TV.

The practical implication: much video distributed in regulated markets needs captions or SDH. AI-generated captions (with human review) make this affordable enough that even small content creators can comply.