Have you ever started typing into a form and had your browser suggest a saved value? HTML can help the browser decide which value belongs in which field. The autocomplete token tel-extension is used for telephone extension.
What tel-extension tells the browser
Telephone extension.
This is a hint, not an instruction to fill a value automatically. Browsers and password managers consider settings, saved data, permissions and other signals before offering suggestions.
Example form field
<form action="/example" method="post">
<label for="detail-field">Extension</label>
<input id="detail-field" name="detail" type="tel" autocomplete="tel-extension">
<button type="submit">Continue</button>
</form>Understanding the example
The autocomplete="tel-extension" attribute labels this field for autofill. Its visible <label> still tells people what to type, and its name attribute determines the key sent when a form is submitted.
Keep extension separate from the main telephone number when appropriate.
A correct token improves convenience but does not prove that the value is accurate. Keep accessible labels and appropriate server-side validation.
Try it yourself
Save the example as an HTML file, and test the field with browser autofill enabled. Inspect the autocomplete value and compare it with the field label. Browser behavior depends on available saved information, so a missing suggestion is not necessarily an HTML mistake.
Common Beginner Mistakes
- Keep extension separate from the main telephone number when appropriate.
- Leaving out the visible label because the browser might autofill the field.
- Treating autofill suggestions as verified or safe data.
Key Takeaways
tel-extensiondescribes telephone extension.- Keep extension separate from the main telephone number when appropriate.
- Autocomplete helps users; it does not replace labeling, accessibility or validation.