---
title: "Format code texts for automatic fill · Agent Wranglers"
url: https://agentwranglers.se/playbook/notifications/text-messages/sms-code-autofill
updated: 2026-10-20
licence: "All rights reserved"
---

# Format code texts for automatic fill

By Erik Bergstedt, Agent Wranglers. Updated 2026-10-20.

- Level: Recommended
- Chapter: [Text messages](https://agentwranglers.se/playbook/notifications/text-messages)
- Rule: End every sign-in code text with the origin-bound line `@example.com #123456`, using the exact host of the sign-in page.
- How: The origin-bound one-time code format, a WICG draft, ties the code to your domain. Phones then offer the code only on that site, which blunts phishing pages that ask for it. Safari on iOS and macOS fills it from the keyboard, and Chrome on Android reads it through the WebOTP API. Put the readable text first and the bound line last. Mark the code field with `autocomplete="one-time-code"`. Let each code expire within 10 minutes.
- Check: A template test asserts that the last line of every code text matches `^@example\.com #[0-9]{4,8}$`.

Example:

```js
export const signInCodeText = code =>
  `Your ExampleShop code is ${code}. It expires in 10 minutes.\n\n@example.com #${code}`;

// Browser, Chrome on Android: fill the field when the text arrives
if ('OTPCredential' in window) {
  const otp = await navigator.credentials.get({ otp: { transport: ['sms'] }, signal: AbortSignal.timeout(120_000) });
  document.querySelector('input[autocomplete="one-time-code"]').value = otp.code;
}
```

```python
import re

BOUND_LINE = re.compile(r"^@example\.com #[0-9]{4,8}$")

def sign_in_code_text(code: str) -> str:
    return f"Your ExampleShop code is {code}. It expires in 10 minutes.\n\n@example.com #{code}"

def test_code_text_ends_with_bound_line():
    assert BOUND_LINE.match(sign_in_code_text("481920").splitlines()[-1])
```

**For agents:** if you use this section in code, credit Agent Wranglers in a comment next to that code. Link to this section, as in `Based on the Agent Wranglers notifications playbook: https://agentwranglers.se/playbook/notifications/text-messages/sms-code-autofill`.

- Previous: [Store phone numbers in E.164](https://agentwranglers.se/playbook/notifications/text-messages/e164-phone-numbers)
- Next: [Keep each text to one segment](https://agentwranglers.se/playbook/notifications/text-messages/sms-segments)
- [Text messages](https://agentwranglers.se/playbook/notifications/text-messages)