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Document Safari's lack of *.localhost domain support #36374

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wadepickett merged 4 commits into from
Nov 21, 2025
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Document Safari's lack of *.localhost domain support #36374

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Initial plan
Copilot Nov 19, 2025
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Add Safari compatibility note to localhost-tld.md
Copilot Nov 19, 2025
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Apply suggestions from code review - clarified "client" app.
wadepickett Nov 19, 2025
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Update aspnetcore/test/localhost-tld.md
wadepickett Nov 21, 2025
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6 changes: 4 additions & 2 deletions aspnetcore/test/localhost-tld.md
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Expand Up @@ -4,7 +4,7 @@ description: Learn how using localhost as top-level domain can make testing easi
monikerRange: '>= aspnetcore-10.0'
ms.author: tdykstra
ms.custom:
ms.date: 08/26/2025
ms.date: 11/19/2025
title: Support for the .localhost top-level domain
uid: test/localhost-tld
---
Expand All @@ -23,7 +23,9 @@ ASP.NET Core's built-in HTTP server, Kestrel, correctly treats any `*.localhost`

## Browser compatibility

While web browsers automatically resolve `*.localhost` names to the local loopback address, other apps might treat `*.localhost` names as regular domain names and attempt to resolve them via their corresponding DNS stack. If your DNS configuration doesn't resolve `*.localhost` names to an address, they fail to connect. You can continue to use the regular `localhost` name to address your apps when not in a web browser.
While most modern evergreen browsers automatically resolve `*.localhost` names to the local loopback address, Safari on macOS doesn't support this feature. In Safari, you should use the regular `localhost` name instead of `*.localhost` domain names.

Some client apps other than Safari and evergreen web browsers treat `*.localhost` names as regular domain names and attempt to resolve them via their corresponding DNS stack. If your DNS configuration doesn't resolve `*.localhost` names to an address, they fail to connect. You can continue to use the regular `localhost` name to address your apps when not in a web browser.

## HTTPS development certificate

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