Measure your blur distance with your front camera — no account needed
Keep both eyes open. Move your device toward your face until the text below just starts to blur, then hold still.
The quick brown fox jumps over the lazy dog. Move your device until this line is just beginning to blur, then hold still.
Everything runs on your device. The video never leaves your browser, and nothing is uploaded or recorded.
Start the camera to calibrate.
Once calibrated, close. The camera measures your pupil gap to a fraction of a percent, which is far finer than the 0.25 D steps people track. The bigger risk is your head turning — that shortens the apparent gap and reads falsely close — so readings are only taken while you're square to the lens.