Battery Status
See your charge level — and why no browser can tell you your battery's health.
How this test works
The Battery Status API reports four things: charge level, whether the device is charging, and estimated times to full and to empty. It updates as those change. What it does not report — and what people almost always arrive looking for — is battery health. Health means design capacity compared against what the battery can hold now, plus how many charge cycles it has been through, and none of those three numbers is available to any browser on any platform. A page claiming to check your battery health from the web is reading exactly the same single figure shown here. The real numbers live in the operating system: coconutBattery or the system report on macOS, powercfg on Windows, and Settings on both mobile platforms.
What the results mean
- Charge
- How full the battery is right now. The only battery figure a browser can read.
- Battery health
- Reported as not exposed. Requires design and full-charge capacity, which no browser provides.
- Cycle count
- Also not exposed. This is the number that actually indicates wear.
- Time remaining
- An operating-system estimate from current draw. It moves a lot as workload changes.
Common problems and fixes
- It says the API is unavailable
- You are in Firefox or Safari, both of which removed it deliberately for fingerprinting reasons. Chromium-based browsers still support it.
- I want to know if my battery needs replacing
- No website can tell you. On macOS use the system report or coconutBattery, on Windows run powercfg /batteryreport, and on phones check the battery settings — all of them expose the capacity and cycle figures a browser cannot.
- The time remaining keeps changing
- It is computed from current power draw, so opening something demanding halves it. Treat it as a rough indication rather than a countdown.
Frequently asked questions
Can a website check my battery health?
No. Health requires design capacity, current full-charge capacity and cycle count, and no browser exposes any of them on any platform. Any site claiming to is showing you the charge percentage under a different name.
Why do Firefox and Safari not report battery status?
Because the combination of level, charging state and time estimates changes slowly and is shared across sites, which made it a useful fingerprinting signal. Both removed it deliberately.
Where do I find real battery health?
In the operating system, never in a browser. macOS: System Report, or coconutBattery. Windows: run powercfg /batteryreport. On iOS and Android the battery settings screen shows it. Those are the only places the capacity and cycle figures are readable.