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

SDH stands for Subtitles for the Deaf and Hard of Hearing. The acronym is used universally across streaming platforms, broadcast standards, and accessibility regulations.

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

• Netflix: "English [SDH]", "Spanish [SDH]", etc.
• Disney+: "English (CC)" or "English [SDH]" depending on title.
• Amazon Prime: "English [Subtitled]" with SDH indicator next to it.
• Apple TV: "English (SDH)" in the audio and subtitles menu.
• HBO Max: "English CC SDH".
• Hulu: "English (SDH)".

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 does both. 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.

Every major streaming platform supports SDH, 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 options labeled "[SDH]" — for example "English [SDH]" or "Español [SDH]".
4. Select your preferred SDH language.

Not all titles have SDH for every language. SDH availability depends on the studio's localisation budget for that title.

Disney+

1. Click the audio/subtitles icon during playback.
2. Look for options labeled "(CC)" or "[SDH]" — Disney+ uses both terms inconsistently across titles.
3. Select the version you want.

Amazon Prime Video

1. Click the speech-bubble icon during playback.
2. Choose from the Subtitles list — SDH-enabled options are tagged with "[Subtitled]" or specifically "(SDH)".

Apple TV / iTunes

1. Press the menu button on Apple TV remote, or click the audio icon in the player.
2. Choose Subtitles → Look for "(SDH)" tagged options.

HBO Max / Max

1. Click the gear icon during playback.
2. Choose Subtitles → SDH options are labeled "CC SDH".

Hulu

1. Click the gear icon → Subtitles & Captions.
2. Look for "(SDH)" labels in the language list.

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 emerged later, in the DVD era of the 1990s and 2000s, when consumer media went international. SDH was designed to solve the global accessibility problem in a format compatible with home video distribution rather than broadcast TV.

Technical reasons

Closed captions in the U.S. broadcast standard have specific limitations: limited fonts, fixed positioning, fixed colors, embedded in the video signal at line 21 (or as auxiliary data in digital TV). SDH is delivered as standard subtitle file formats (SRT, VTT, TTML) which support richer styling, positioning, and multiple fonts.

Editorial reasons

U.S. closed captions historically had specific conventions around music notation (treble clef symbols), positioning rules, and content choices. SDH developed its own conventions optimised for international distribution — more flexible language handling, different formatting standards.

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. Netflix, Disney+, etc. blur the terminology because the underlying technology is the same. The labeling distinction (CC vs SDH) is often editorial — CC for U.S.-broadcast-style captioning conventions, SDH for international-distribution-style.

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. The international standard for streaming originals — Netflix, Disney+, Apple TV+ originals all ship with this matrix.
• 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. Industry pricing in 2026 is roughly:

• AI-generated captions / SDH (with human review): $1-3 per minute
• Human-produced subtitles: $5-12 per minute
• Human-produced SDH: $7-15 per minute
• Human translation + SDH for foreign language: $10-25 per minute

For a 90-minute film, SDH in 5 languages can easily cost $5,000-10,000 in human-produced content. Streaming platforms typically include SDH for major releases because the cost is small relative to production budgets, but smaller producers often skip non-English SDH.

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 — Most common SDH delivery format for streaming uploads. 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. — ADA, Section 508, FCC: Captions required for most broadcast and online video. SDH or CC both satisfy the requirement.
• 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. SDH satisfies this.
• EU — European Accessibility Act (EAA, 2025): Requires accessibility features including captions/SDH for digital products and services across the EU.
• UK — Equality Act 2010: Requires reasonable accommodations for accessibility, interpreted to include captions on most public-facing video.
• Canada — Accessible Canada Act: Federal-level accessibility requirements; provincial laws (AODA in Ontario) add specific captioning requirements.
• Australia — Disability Discrimination Act + Broadcasting Services Act: Captioning quotas for broadcast TV; growing pressure for online video parity.

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