Attachment Reminder is a Chrome extension that stops you sending a Gmail message that mentions an attachment without one. It watches your compose window for phrases like "see attached" or "I have attached", and if you press Send with nothing attached it interrupts once and offers to attach the file.
How it decides
Detection is a keyword and phrase list, not a language model. It looks for attachment intent in what you have written: "attach", "attached", "attaching", "see attachment", "please find attached", "enclosed" and their common variants.
A light tense check keeps it from firing on references to a past attachment. "As I attached last time" and "the file I sent previously" both name an attachment, but neither promises one now, so neither triggers a warning.
When it does fire, the prompt appears next to the Send button with two choices: attach a file, or send anyway. Choosing send anyway is remembered for that conversation, so replying again in the same thread will not ask twice.
When it stays silent
Which is almost always. If you did not mention an attachment, or you already attached one, nothing happens at all. No badge, no notification, no icon lighting up. For the overwhelming majority of emails you will never know it is installed.
Permissions
mail.google.com only. It runs on Gmail and nowhere else. It cannot see any other site you visit.
About Attachment Reminder
Does it work with Outlook or Apple Mail?
Not yet. This version targets Gmail on the web. The detection logic is kept separate from the Gmail specific code, so adding another mail client is packaging work rather than a rewrite.
Does it read my email?
It reads the text in the compose window you are actively typing in, inside your browser, to look for attachment wording. Nothing is stored, and nothing is sent anywhere. There is no server to send it to.
Will it fire on every email that says "attached"?
No. It only interrupts when attachment wording is present and no file is attached. If you attached the file, it says nothing.
Does it work on replies and forwards?
Yes, across all Gmail compose surfaces: new messages, replies, reply all, forwards, the pop out window and full screen compose.
Installing? The four step guide covers it.