Question 1

What does the RAM Checker show?

Accepted Answer

The RAM Checker displays three values from the performance.memory API (Chrome/Chromium only): JS Heap Used (memory currently in use by JavaScript objects), JS Heap Total (total allocated heap space), and Heap Limit (maximum allowed heap size). It also shows navigator.deviceMemory if available, which reports the device's approximate physical RAM. The allocation speed test allocates and fills a 50MB Float32Array to measure memory bandwidth.

Question 2

Why does this only work in Chrome?

Accepted Answer

The performance.memory API is a non-standard Chrome extension to the Performance interface and is intentionally not available in Firefox or Safari. Mozilla and Apple have declined to implement it citing privacy concerns — memory usage patterns could potentially be used for fingerprinting. Chrome exposes it only in non-cross-origin contexts. The allocation speed test and navigator.deviceMemory still work in most modern browsers.

Question 3

What is navigator.deviceMemory?

Accepted Answer

The Device Memory API (navigator.deviceMemory) returns the approximate amount of device RAM in gigabytes, rounded to the nearest power of 2 (e.g., 0.25, 0.5, 1, 2, 4, 8). The maximum value reported is 8 GB regardless of actual RAM to prevent fingerprinting. It is supported in Chrome, Edge, and Samsung Internet but not in Firefox or Safari. It allows websites to serve lighter resources to low-memory devices.

Question 4

What does the JS Heap Used value mean?

Accepted Answer

JS Heap Used represents the amount of memory currently occupied by live JavaScript objects including strings, arrays, objects, closures, and compiled code. This value changes continuously as objects are created and garbage-collected. High heap usage relative to the heap limit may cause performance issues or tab crashes. Running this test alongside heavy web apps can reveal memory leaks where heap usage grows continuously without returning to baseline.

Question 5

How can I reduce browser memory usage?

Accepted Answer

Browser memory usage is affected by the number of open tabs, installed extensions, size of loaded images and media, JavaScript application complexity, and memory leaks in web applications. To reduce usage: close unused tabs, disable or remove extensions, avoid keeping large media-heavy pages open indefinitely, and use the browser's task manager (Shift+Esc in Chrome) to identify which tabs are consuming the most memory. Some browser flags can also adjust memory limits.

RAM Checker

Browser Memory APIs

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