Battery Tester

• Step 1: Open the battery tester on a supported browser. The Battery Status API is supported by Chromium-based browsers including Google Chrome, Microsoft Edge, Opera, Brave, and Samsung Internet. It is not supported by Firefox (which removed the API in 2016 for privacy reasons) or Safari (which never implemented it).

• Step 2: The battery information loads automatically. When you open the page on a supported browser and device, the tool reads battery information immediately without requiring any button press. If you see "Loading battery information...", allow a moment for the browser to retrieve the data.

• Step 3: Read your battery status. The tool displays:

• Battery level: Your current charge percentage from 0% to 100%.

• Charging status: Whether your device is currently plugged in and charging, or running on battery power.

• Charging time: If plugged in, the estimated time in minutes or hours until the battery reaches full charge.

• Discharging time: If running on battery, the estimated time in minutes or hours until the battery is depleted at the current usage rate.

• Step 4: If the tool shows that the Battery Status API is not supported, you are using Firefox, Safari, or a browser that has removed or blocked this API. To check battery status on an unsupported browser, use your operating system's built-in battery tools instead.

The Battery Status API provides four pieces of information that the tester displays:

Battery Level (Percentage)

The battery level is reported as a value from 0 to 1 (converted to 0% to 100% for display). This is your current state of charge at the moment the page loads, and it updates automatically as the battery charges or discharges while you remain on the page.

Note: Modern browsers deliberately round battery percentage values slightly for privacy reasons. The displayed value is close to your actual battery level but may be rounded to the nearest 5% or some other increment depending on the browser version and settings. This rounding was implemented after researchers demonstrated that precise battery values could be used for user fingerprinting and tracking across websites.

Charging Status

The charging status shows a simple true or false value: either the device is currently connected to a power source and charging, or it is running on battery power alone. This is useful for quickly confirming that a charger connection is being recognized by the device.

If you plug in a charger and the charging status does not change to "charging," the issue may be with the charger, the charging port, the charging cable, or a software issue preventing the device from recognizing the power source.

Charging Time

When the device is plugged in and charging, the charging time shows the estimated number of seconds (converted to minutes and hours for display) until the battery reaches full charge. This estimate is provided by the battery management system in your device hardware and varies based on current charge rate, battery temperature, and battery age.

A value of Infinity for charging time means the device is plugged in but not actually drawing charge (or the device's battery management system cannot estimate the remaining time), which can indicate a slow charger, a faulty charging cable, or a charging port issue.

Discharging Time

When running on battery power, the discharging time shows the estimated time until the battery reaches zero. This is calculated from the current battery level and the current discharge rate based on what the device and its applications are currently doing. Battery-intensive tasks (video, gaming, high brightness) shorten this estimate. Light usage (reading, low brightness) extends it.

A value of Infinity for discharging time when the device is plugged in is normal and expected: it means the battery is not discharging.

Understanding which browsers support the Battery Status API helps you know whether to expect results from the tester.

Supported browsers

• Google Chrome: Supports the Battery Status API. The API is available through navigator.getBattery() in Chrome on all platforms where battery information is accessible (Windows, macOS, Linux, Android). Note that Chrome has implemented some privacy protections that may round or limit the precision of reported values.

• Microsoft Edge: Chromium-based Edge (Edge 79 and later) supports the Battery Status API.

• Opera: Supports the Battery Status API as a Chromium-based browser.

• Brave: Supports the Battery Status API but may have additional privacy settings that limit the API's output depending on your Brave shields configuration.

• Samsung Internet: Supports the Battery Status API on Android devices.

Browsers that do not support the API

• Mozilla Firefox: Firefox supported the Battery Status API until 2016, when it removed the implementation due to privacy and fingerprinting concerns. The developers determined that the combination of battery level, charging status, and time estimates created a sufficiently unique signature to track users across websites without their knowledge. Firefox no longer returns battery data from this API.

• Apple Safari: Safari never implemented the Battery Status API. Apple's approach to web APIs prioritizes privacy and Safari has historically declined to implement APIs with fingerprinting potential.

• Internet Explorer: Not supported.

Operating system considerations

The Battery Status API reads battery information provided by the operating system. On desktop computers that do not have a battery (standard desktop PCs without a UPS), the API may return data indicating the system is "charging" indefinitely or may not return meaningful battery data. On laptops, tablets, and smartphones, it provides accurate battery information.

If the tester shows "not supported" on Chrome or Edge, check whether your desktop system has a battery. Desktop computers without batteries provide no meaningful battery data to the API even if the browser supports it technically.

The Battery Status API is a web standard defined by the W3C (World Wide Web Consortium) that allows web pages to request battery information from the device through the browser. The technical mechanism works as follows:

• The browser calls navigator.getBattery(), which returns a Promise that resolves to a BatteryManager object.

• The BatteryManager object exposes four properties:

• battery.level: A number from 0 to 1 representing battery charge (0 = empty, 1 = fully charged).

• battery.charging: A boolean, true if plugged in and charging, false if on battery.

• battery.chargingTime: Seconds until fully charged (Infinity if not charging or time cannot be estimated).

• battery.dischargingTime: Seconds until empty (Infinity if plugged in).

The API also fires events when any of these values change (levelchange, chargingchange, chargingtimechange, dischargingtimechange), allowing the tester to update displayed values in real time without requiring a page refresh.

What the API does NOT provide

The Battery Status API is specifically designed to expose only the four values above. It does not provide:

• Battery health or degradation level (original capacity vs current capacity)

• Battery cycle count

• Battery manufacturer information

• Battery model or chemistry type

• Precise voltage or current readings

These values are deliberately withheld from browser APIs because they would too precisely identify individual devices for fingerprinting purposes. To access battery health information, operating system tools must be used instead.

Battery health (the ratio of your battery's current maximum capacity to its original design capacity) is not accessible through browser APIs. This is true for all browsers and is not a limitation of Thetoolity's battery tester specifically. It is a deliberate restriction across the entire web platform for privacy reasons.

To check real battery health, use your device's operating system tools:

Windows Laptop

Open a Command Prompt or PowerShell as administrator. Type: powercfg /batteryreport and press Enter. Windows generates a detailed battery report HTML file (usually saved to your user folder) that includes battery design capacity, current full charge capacity, battery cycle count, and usage history. The ratio of current full charge capacity to design capacity is your battery's health percentage.

macOS

Hold the Option key and click the battery icon in the menu bar to see "Condition" (Normal, Replace Soon, Replace Now, or Service Battery). For more detail: open System Information (About This Mac, System Report), then navigate to Power and look for Cycle Count, Condition, and Full Charge Capacity versus Design Capacity.

iPhone and iPad

Settings, Battery, Battery Health and Charging. Apple shows the maximum capacity as a percentage of original design capacity and whether the battery is supporting peak performance.

Android Smartphones

Battery health access varies by manufacturer. Samsung: Samsung Members app, Get Help, Interactive Checks, Battery. Google Pixel: Settings, About Phone, Battery information. Third-party apps (AccuBattery) can estimate battery health by measuring actual charge capacity. Note: Android does not expose a standard battery health percentage through Settings in most manufacturer implementations.

Why knowing battery health matters

A battery at 80% health can hold 80% of its original charge. A phone that originally lasted 10 hours on a charge now lasts approximately 8 hours. At 70% health, it lasts approximately 7 hours. Knowing your battery health helps you decide when to replace a battery versus when poor battery life is due to software or usage patterns.

Battery draining faster than expected

Causes: high screen brightness, background app activity, weak signal causing radio modules to work harder, battery aging reducing total capacity, or running processor-intensive tasks. This is normal battery behavior rather than a hardware defect in most cases, but a battery that drains significantly faster than when new (for example, from 10 hours to 4 hours in two years) likely has meaningful capacity degradation.

Battery not charging to 100%

Modern devices implement battery charge limiting as a health feature. Both iOS (Optimized Battery Charging) and many Android devices (Adaptive Charging) and laptops deliberately stop charging at 80% to 85% under some conditions to reduce battery degradation from remaining at 100% charge for extended periods. This is not a malfunction.

Battery percentage jumping unexpectedly

If the displayed battery percentage suddenly jumps up or down by large amounts (for example, from 45% to 20% instantly), the battery management system's capacity estimate has become inaccurate. A full calibration cycle (discharge to near empty, then charge to 100% uninterrupted) can help recalibrate the battery management system, though modern lithium batteries benefit from this less than older nickel-metal hydride batteries.

Device not recognized as charging

If you plug in a charger but the Thetoolity battery tester shows charging status as "not charging," verify the charger is properly seated, try a different cable, try a different power outlet, and try a different charger if available. If the device still shows not charging with a known-good charger and cable, the charging port may have debris or physical damage.

Device showing "charging" but not actually gaining charge

Some devices show a charging indicator when connected to a power source but do not actually gain charge if the power source is insufficient. Charging a phone with a 5W charger while it is under heavy use (navigation, gaming, hotspot) can result in a net discharge even while "charging." The battery percentage slowly drops despite being plugged in. A more powerful charger or reduced device usage resolves this.

The Thetoolity browser-based battery tester and a full battery health check serve different purposes and provide different information. Understanding both helps you use the right tool for each situation.

What the browser battery tester provides

• Current charge level (percentage right now)

• Current charging status (plugged in or on battery)

• Estimated time to full charge (when charging)

• Estimated time remaining (when on battery)

These values change in real time and tell you the current state of your battery. They answer the question "what is my battery doing right now?"

What a battery health check provides

• Maximum charge capacity as a percentage of original design capacity

• Cycle count (how many complete charge-discharge cycles the battery has gone through)

• Battery condition (normal, service recommended, or critical)

• Degradation rate over time

These values change slowly over months and answer the question "how much capacity has my battery lost over its lifetime?"

The browser battery tester is useful for quick, real-time monitoring and charger verification. The OS battery health tools are necessary for understanding long-term battery degradation and deciding when a battery needs replacement.

Thetoolity brings together a growing collection of free, fast, and clean online tools for anyone who needs quick device information without navigating through settings menus. Our battery tester uses the Battery Status API to display charge level, charging status, and time estimates instantly in supported browsers.

No accounts. No subscriptions. No cluttered interfaces. Just a clean, instant battery status check.

Explore the full collection at Thetoolity.com and find generators, converters, calculators, checkers, and testers, all free and all instant.

Note: The Battery Status API requires a Chromium-based browser (Chrome, Edge, Opera). Firefox and Safari do not support this API. For battery health information beyond charge level, use your device's operating system battery tools.