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Receiving devices and apps: what every screen must do

The Standard applies to any device that has a screen, a loudspeaker or a vibration motor, alone or in combination: phones and watches, televisions and set-top boxes, in-car displays, digital signage, outdoor warning sirens, building alert systems (fire alarm panels, strobe and horn notification appliances, evacuation announcements, lobby displays, the building's own lighting, and the screen, the chime and the cabin light of a lift) and smart lights. A device renders the channels it has and leaves the others to the devices around it; together they carry one rhythm.

What a fully accessible alert screen looks like

Here is the layout, element by element. Below is one alert, a Water alert at Severe (ACT NOW), drawn on a phone, a television and a watch. The numbers on each screen match the list underneath.

Phone screen, a Water alert at Severe. 4: the whole screen is the ACT NOW colour. 6: a small light cue at the top, and 7: the sound icon. 5: the word ACT NOW above 3 white triangles. 2: a large flood pictogram. 1: the signed video, the authority’s own clip, with the signer fully in frame. 3: the caption band, “FLOOD. Go up high. Stay there.”, with a tell me more control. 8: a replay control, the sender and the time.

Phone, portrait

Television screen, the same Water alert. 4: the whole screen is the ACT NOW colour. 6: the light cue and 7: the sound icon along the top. 1: the signed video fills the left half, signer fully in frame. On the right, 5: the word ACT NOW above 3 white triangles, 2: the flood pictogram, and 3: the caption band, “FLOOD. Go up high. Stay there.”, with a tell me more control. 8: replay, sender and time along the bottom.

Television, 16:9

Watch screen, the same Water alert. 4: the whole face is the ACT NOW colour. 2: the flood pictogram. 5: the word ACT NOW above 3 white triangles.

Watch, 1:1Element 1, the signed video, is absent on the watch.

A device renders the channels it has (the watch shows the pictogram, the triangles and the rhythm; the television adds the signed video and the sound) and together they carry one rhythm.

  1. 1

    The signed video

    The authority's own signed video, carried in the alert as a CAP resource. It is shown large, with the signer fully in frame, never cropped and never covered. On the watch this element is absent.

  2. 2

    One giant pictogram

    One large picture of the hazard, so the danger reads at a glance.

  3. 3

    The hazard word and the action

    The hazard word and what to do, in simple words a child can understand: short sentences, no jargon, on white-on-black caption bands. The authority's full text stays one "tell me more" away.

    FLOOD. Go up high. Stay there.

    Tell me more

    The authority’s own text it replaces (example): Flash Flood Warning in effect for this area until 18:00. Persons in low-lying areas should move to higher ground immediately and avoid flooded roads and underpasses.

  4. 4

    The severity colour, as the wash

    The severity colour fills the screen behind everything. It never works alone: the triangles and the word say the same level.

  5. 5

    The severity triangles and word

    White triangles whose count is the severity (1 at BE CAREFUL, 2 at DANGER COMING, 3 at ACT NOW), with the severity word above them.

  6. 6

    The light cue

    A light cue on the shared rhythm, inside the photosensitivity limits: never more than 3 flashes or 6 state changes per second, with a steady-light path for people who are photosensitive. A bounded indicator, never a full-screen flash.

  7. 7

    The sound

    The sound plays the same shared rhythm that the light shows and the hand feels, so the people nearby hear what the screen shows.

  8. 8

    Replay, sender and time

    A replay control (on a screen without controls, a repeat on a schedule), who sent the alert, and when. When the danger ends, the all-clear: a green wash, the circle mark, calm words naming what ended, and no alarm.

Television, signage and broadcast overlays

Televisions, set-top boxes and digital signage are inside the Standard’s device scope. Some of these screens have no buttons, and a broadcast overlay often cannot add sound to the programme. A broadcaster designing an overlay asked us what the screen above becomes there. Four rules answer, drawn on the same television and marked A to D.

Television screen as a broadcast overlay, the same Water alert. The whole screen is the ACT NOW colour. C: a small bounded light cue at the top, steady or slow. B: the sound is the broadcaster’s choice and the vibration goes to a paired phone or watch. The signed video fills the left half. On the right, the word ACT NOW above 3 white triangles, the flood pictogram, and D: the caption band, “FLOOD. Go up high. Stay there.”, the authority’s template, unchanged. A: along the bottom, the alert repeats while active, at least every five minutes, with the full text in every cycle, beside the sender and the time.

Broadcast overlay, 16:9, marked A to D
  1. A

    A repeat on a schedule, in place of replay

    Where the screen has no replay and no "tell me more" control, as on linear television, signage and public displays, the whole alert repeats on a schedule while it is active. The operator declares the interval, and it is never longer than five minutes. Every cycle shows the authority's full text, as a second screen or a crawl, so "tell me more" becomes "it comes back with everything". An all-clear is shown at least twice. Streaming and IPTV screens that can offer controls keep the replay and the "tell me more" control.

  2. B

    An overlay keeps every picture; the sound is the broadcaster's decision

    A graphics overlay that cannot add sound to the programme audio conforms when it carries the complete visual channel: the signed video with the signer fully in frame and never cropped or covered, one large pictogram, the hazard word and the action on caption bands, the severity wash never alone but with the triangles and the severity word, the light cue, the sender and the time, and the all-clear as a green wash with the circle mark. Whether sound plays is the broadcaster's decision. The vibration goes to a paired phone or watch, kept in step by the alert's own CAP identifier. Emitted on three senses, survivable on one: that is why a silent overlay can conform. What it may never do is shrink the alert to a text crawl.

  3. C

    Light that never floods the screen

    On a television or a public display the light cue never becomes full-screen flashing: at most three flashes per second, in a bounded area rather than the whole screen, and a steady or slow pulse rather than any strobe. Three flashes per second is the general flash threshold of WCAG 2.3.1; broadcasters also observe ITU-R BT.1702 and their national rules. The light follows the shared rhythm of the three channels rather than competing with it.

  4. D

    A relay never rewrites

    A relay shows the authority's text unchanged. The action in simple words a child can understand comes from the alerting authority's own pre-approved template for that hazard and action, named in the CAP message by a template identifier or event code, never from a rewrite downstream. Where no template exists, the relay shows the authority's instruction exactly as sent and does not simplify it: the fix for hard words is a better template upstream. Never guess, never rewrite.

The same alert at every level

The same Water alert at all four levels. The colour, the number of triangles and the word change together. Across the three danger levels the picture and the rhythm stay the same; at SAFE NOW the alarm rhythm stops and the calm all-clear takes over.

  • SAFE NOW

    no triangles, the circle mark

  • BE CAREFUL

    1 triangle

  • DANGER COMING

    2 triangles

  • ACT NOW

    3 triangles

Right and wrong

Wrong: colour only

A plain ACT NOW colour. No level, no danger, nothing for a colour-blind reader.

Right: the Standard’s layout

Colour plus shape plus word: the pictogram, 3 triangles and ACT NOW.

Colour never works alone

Is your alert screen fully accessible?

Twelve yes-or-no questions for implementers. Every answer should be yes.

  1. Is the authority's signed video, carried as a CAP resource, shown large, with the signer fully in frame and never cropped or covered?
  2. Is there one giant pictogram for the hazard?
  3. Are the hazard word and the action given in simple words a child can understand, on white-on-black caption bands, with the full text behind a "tell me more" control?
  4. Is the severity colour the wash behind everything, and never the only sign of the level?
  5. Do white triangles show the severity by their count, with the severity word above them?
  6. Is the light cue a bounded indicator inside the photosensitivity limits, never a full-screen flash?
  7. Does the sound play the shared rhythm?
  8. Does the screen show who sent the alert and when?
  9. Can the alert be replayed?
  10. Where the screen has no replay control, does the whole alert repeat while it is active, at a declared interval of five minutes or less, with the authority's full text in every cycle?
  11. Are the simple words the authority's own pre-approved template, shown unchanged and never rewritten downstream?
  12. Is the all-clear a green wash with the circle mark, calm words naming what ended, and no alarm?

Captured from the reference app

Real screenshots of Deaflare, the reference app, taken on an iPhone simulator on 9 October 2026: the same drill alert at three severity levels, and a second hazard at Extreme. Colour, triangles and the severity word move together; the hazard word, the pictogram and the controls stay where they are.

Deaflare full-screen takeover for a test flood alert at Extreme: a red wash, the words TEST ONLY and This is a test, the severity word EXTREME, three white triangles, the hazard word FLOOD on a black band, a large wave pictogram, a line saying the alert repeats until I UNDERSTAND is pressed, the expiry time, and the buttons Tell me more, Send to someone, Listen and I understand.
Flood at Extreme, a test alert as Deaflare renders it: severity colour, severity word, three triangles, hazard word, pictogram, replay and understanding controls.
Deaflare full-screen takeover for a test storm alert at Severe: an orange wash, the words TEST ONLY and This is a test, the severity word SEVERE, three black triangles, the hazard word STORM on a black band, a large spiral storm pictogram, a line saying the alert repeats until I UNDERSTAND is pressed, the expiry time, and the buttons Tell me more, Send to someone, Listen and I understand.
Storm at Severe, the same drill one level down: orange instead of red, dark triangles instead of white, a different hazard word and pictogram, everything else in the same place.
Deaflare full-screen takeover for a drill at Moderate: a yellow wash, the words TEST ONLY and This is a test, the severity word MODERATE, two dark triangles and one faint one, the word TEST on a black band, a test-tube pictogram, a line saying the alert repeats until I UNDERSTAND is pressed, the expiry time, and the buttons Tell me more, Send to someone, Listen and I understand.
The drill at Moderate: yellow, two triangles out of three, and the drill's own honest face, the word TEST, so nobody mistakes a practice screen for a hazard.
Deaflare full-screen takeover for a test earthquake alert at Extreme: a red wash, the words TEST ONLY and This is a test, the severity word EXTREME, three white triangles, the hazard word EARTHQUAKE on a black band, a large mountain pictogram, a line saying the alert repeats until I UNDERSTAND is pressed, the expiry time, and the buttons Tell me more, Send to someone, Listen and I understand.
Earthquake at Extreme: the same red and the same three white triangles as the flood, so severity reads the same across hazards; only the word and the pictogram change.