Touch delay check
Measure a phone's touch delay
A timed test on a phone is only as good as the phone's reaction to a touch. This page measures it with two phones and a table. It takes about 15 minutes for each phone. What you tap and type stays in your browser: nothing is sent or saved.
What you do
What you need
- The phone or tablet to measure, with the browser people will use on it.
- A second phone with slow-motion video. 120 frames per second is the least that counts, and 240 is better.
- A table, good light, and about 15 minutes.
The rule
A phone passes when 20 or more taps, filmed at 120 frames per second or more, spread by no more than 10 ms (the standard deviation of the delays). Timed tests open to phones when at least 2 phones pass, with at least 1 iPhone and 1 Android phone. Tablets are counted separately.
The delay is the time from the touch to the screen change. The mean says how late a phone reacts. The spread says how much that changes from tap to tap, and the spread is what limits a timed test: a steady delay moves every response by the same amount, and phones have their own norms.
Set up the two phones
Lay the phone to measure flat on the table. Put the second phone beside it, low, pointing at the first phone from the side, so its camera sees the screen and your fingertip. Switch it to slow motion.
Start filming, then start the taps
Press Start the taps on the phone to measure. Tap anywhere on the screen about once a second, 20 times or a few more. Each tap turns the screen from white to black, or from black to white.
Press Done, then stop filming
Done is the button at the top of the tapping screen. It does not count as a tap.
Read the frames
Open the video in an app that steps one frame at a time. For each tap, write down the frame where your finger first touches the glass, and the frame where the screen changes color.
Type the frame numbers
Type them into the table below, with the camera's frames per second. The page works out each delay in milliseconds, the mean and the spread.
Copy the block of data
At the end the page gives one block of data for this phone. It is the phone's entry for the device timing record.
Run the check
Start the camera on the second phone first. Then press the button, tap 20 times or a few more, and press Done.