An OLED panel wears where bright, unchanging content sits. Candela keeps that record per display and acts on it, which is two separate jobs: Health watches and OLED Care dims.
Settings has an OLED Care pane with one card per external display. Opening a card gives that display its own page, and the switch at the top is Enroll this display in OLED care. Enrolling applies the recommended settings: dim to 50% after 5 idle minutes, dim while the screen is locked, and count hours of use. Nothing changes until the display has actually been idle for a while, everything can be changed afterwards, and nothing outside that display is touched.
Enrollment is per display, and it gates all of OLED care: a display you never enroll is never dimmed, never measured, never attributed by app and never counted for hours. Turning a measurement switch on for an unenrolled display records nothing, so enroll it first.
All of it is on the display's OLED Care page, under Dimming. Idle, unfocused, blackout and regional dimming draw dark overlays. Lock dimming uses a temporary brightness adjustment because overlays cannot cover the macOS lock screen. Your saved brightness setting stays unchanged.
- Idle dim. After a set number of minutes with no keyboard or mouse activity anywhere on the Mac, the display dims to a level you choose. Video playback, calls and anything else that holds the screen awake postpone it.
- Dim while the screen is locked. Same brightness as the idle dim. A key or click lifts it while the screen stays locked, and it comes back after the idle time.
- Turn the screen black after longer. A full blackout after a longer idle period. The click that wakes it is discarded, so nothing is clicked by accident. A key press wakes it too, but that key reaches whichever app you were using.
- Dim while this display has nothing in focus. For the display you are not working on. Only clicking into it brings it back, not typing elsewhere.
- Automatic static-region dimming. Bright, stable regions in background windows can dim a little while you work. Your foreground app stays undimmed across displays, as does the entire window under your pointer. After the pointer leaves a window, it stays clear for two seconds, then eligible regions fade back to their dimmed level over one second. Other background windows remain protected, including other windows belonging to the same app. Full-screen content and anything holding the display awake suspend this protection. Regional dimming is also withheld while Candela itself is foreground, because its windows are excluded from capture. This setting is off by default and needs both measurement settings on the Health pane.
In the menu bar panel, the care status line under an enrolled display's name is itself the control: click it for Pause Dimming for 15 Minutes, Pause Dimming for 1 Hour and Pause Dimming Until…, which opens a window for choosing a date and time up to a year ahead. The display's OLED Care page has the same three choices in its Pause Dimming menu under Dimming. While a pause runs, the status reads "Dimming paused until" and the end time, and Resume Now ends the pause early. A mirrored display, or one showing a checkup field, is already held undimmed for that reason, so its OLED Care page keeps naming that reason during a pause.
A pause immediately lifts idle, unfocused, blackout, regional and lock dimming for that display. Health measurement and hours keep running under their usual conditions. It does not change enrollment, saved dimming settings or macOS sleep behavior.
The pause follows the display across reconnects and its deadline includes time spent asleep. Dimming resumes with a fresh idle interval, and regional protection gathers fresh evidence. Quitting Candela, resetting its settings or turning off that display's enrollment clears the pause.
The detector compares spatial fingerprints from the existing once-per-minute captures. A region needs six matching samples spanning at least five minutes, bright content, and a stationary window fully covering the cell. A changed sample or window owner restarts that region's evidence. A cell shared by multiple windows is left alone.
An eligible region normally receives a 15% dark overlay. Once at least 30 exposure samples have accumulated, regions above the panel's average recorded exposure receive a proportional increase, capped at 25% at twice the average. History alone never makes a dark, changing, or actively used region eligible. This is an exposure-based policy, not a calibrated prediction of physical wear.
Dimming tapers inward at a region's edges and corners to reduce visible box boundaries. The interior retains its eligible depth; narrow or isolated regions receive less dimming. This taper does not make additional cells eligible and does not change the uniform idle-dimming or exposure-compensation masks.
A gap longer than 90 seconds, a failed capture, sleep, display reconfiguration, or disabling the required settings discards temporary detection evidence. Protection needs fresh samples before it can resume. Your cumulative exposure history is retained and does not automatically decay; it begins when you enable measurement and cannot account for earlier use of the display.
The detector retains only coarse brightness values and per-region fingerprints, not screenshots. It can miss motion between samples or changes too small to alter a fingerprint. A paused video or photograph is still static content; focus is a useful signal, not proof of what you are looking at. Keep regional dimming off when judging colors or brightness. Other apps' overlays that macOS omits from capture cannot be accounted for, and the exposure map is not a measurement of the panel's actual light output.
The OLED Care pane also has a Screen Chrome section that applies to the whole Mac rather than one display: one switch each for automatically hiding the menu bar and the Dock, the two pieces of interface that sit in the same pixels for hours. These write the same system settings you would set in System Settings, and Candela says so if macOS does not take the change.
Measurement lives on the Health pane, per display, with a switcher when more than one display is attached. Two independent switches:
- Measure how bright each part of this display is. Needs macOS to grant Screen Recording. It takes one reading a minute while the display is awake and in use, reduces each to a coarse grid of mean brightness (24 cells across by 10 down), and accumulates that into the exposure map. No image is stored and nothing on your screen can be reconstructed from a grid that size. This is the only place in the app that asks for Screen Recording. Off by default.
- Note which apps are on this display. Needs no permission. It reads each on-screen window's position and the name of the app that owns it, never window titles and never their contents. This is what puts an app's name next to an area of the display. On by default.
Both pause while the Mac is running on battery at 20% charge or less.
The Heat Map window (from the display's OLED Care page, or Open Heat Map on a Health card) is the map itself, in the panel's own geometry, so a rotated display accumulates wear where the wear actually is. It states which of three things it is showing:
- Measured. Enough readings recorded to say something. Figures are relative to this display's own average, never an absolute luminance.
- Not enough readings yet. Under 30 readings, no figures are shown at all, because there is nothing to be right about yet.
- Estimated: brightness is not being measured. Measuring is off, so nothing comes from the screen itself. What remains is window geometry: which app held which part of the display, and for how long. There is no heat map in this state, because a map drawn without readings would imply a currency it does not have.
If measuring is on but macOS has withdrawn Screen Recording, the window says so rather than quietly recording nothing. History recorded before that point is kept.
Count hours of use, also on the Health pane, counts while the display is awake and not mirrored, and keeps the count per display even when it is unplugged. One honest limit: a display switched off at the monitor itself can still be counted, because macOS reports a blanked display as awake and there is no layer at which the difference is observable.
Each display's card on the Health pane has Export provenance... and Copy summary. A provenance record bundles that display's hours, exposure history and checkup runs into one file carrying a hash of its own contents, so it can go with the display when you sell or return it. The record states in its own text that its data is self-reported: it corroborates, it does not certify. Check a provenance file on the Checkup pane verifies that a record somebody sends you still matches its hash. Nothing is sent anywhere by the app itself.
Some monitors accept commands over the cable but answer every read with zeros. None of OLED care depends on reading from the display. The dimming is an overlay Candela draws, the exposure readings come from the screen contents, and the hours come from macOS, so a write-only panel gets the same care as any other. What such a panel cannot do is tell Candela its current brightness, so the brightness value you see is the last one Candela sent, tracked and saved. Which sort of panel you have is stated on the display's Diagnostics page.
Hold Shift while launching Candela and, for that session, no display is dimmed, no hours are counted and no measurements are taken. Everything recorded before that session is kept, and the panes that would otherwise describe behaviour that is not happening say so on screen.