Yardline handles the handoff between a building supplier and a contractor: a truck arrives on site, someone has to confirm what came off it, note what is missing or damaged, and sign. That someone is usually a crew lead standing on a roof or in a driveway, in gloves, with one bar of signal, who has never heard of Yardline and has no interest in creating an account.

So the crew gets a link instead. Tap it, see the delivery, mark it received. No password, no app install, no sign-up. The rest of this post is about making that link safe to hand out by text message, and sturdy enough to work when the phone is offline.

Text sizes have a 14px floor. The people using this are often outside, in bright light, and not looking closely.

What a link like this has to guarantee

A link is a password that travels in plain sight: in SMS threads, group chats, forwarded screenshots. Before writing any code I listed what it must and must not allow:

It opens one delivery and nothing else.…