Tools that do one thing

Full-screen test patterns for a new monitor, phone or TV: dead pixels, uneven light, banding, ghosting and how many pictures a second you are really getting.

Listens through your microphone and shows which pitches are loudest, live, with the frequency and musical note of the strongest one.

Play a sound from each speaker in turn, or send it circling round your head, to check headphones, stereo, 5.1 and 7.1 systems.

Play a tone, a sweep or noise through the left, right or both speakers, to test speakers, headphones, rooms and hearing.

A password made of random everyday words, easy to remember and type, with an honest measure of how hard it is to guess.

A strong password in short readable chunks, like the ones Apple suggests, with an honest measure of how hard it is to guess.

Make a photo small enough for an email or an upload form that keeps rejecting it, and leave behind the hidden note of where it was taken.

A QR code that joins a Wi-Fi network, saves a contact, opens a link, fills in a bank transfer — or just holds your text.

Flip a coin, roll dice, pick a number or draw names from a hat. Every outcome is exactly as likely as every other.

Words, characters, sentences and reading time for any text, and whether it fits a text message, a post or a search result.