---
title: "Link preview fetchers (4) — AI Crawler Index"
description: "Read your Open Graph tags when someone shares a link. Blocking these is almost always an accident."
canonical: "https://www.pathwren.workers.dev/category/preview.html"
url: "https://www.pathwren.workers.dev/category/preview.md"
format: "markdown"
source: "the bytes of /category/preview.html, in the build that wrote the page"
generator: "surfaces/ai-crawler-index/build.py"
generated: "2026-09-03T06:29:54+00:00"
license: "CC0-1.0"
---

# Link preview fetchers

> Read your Open Graph tags when someone shares a link. Blocking these is almost always an accident.

Read your Open Graph tags when someone shares a link. Blocking these is almost always an accident.

| Crawler | Token | Operator | Cost of blocking |
| --- | --- | --- | --- |
| [facebookexternalhit](https://www.pathwren.workers.dev/crawler/facebookexternalhit.html) | `facebookexternalhit` | Meta | Severe and usually accidental. Your links share as bare grey boxes with no title, image or… |
| [GoogleMessages](https://www.pathwren.workers.dev/crawler/googlemessages.html) | `GoogleMessages` | Google | Your links appear as bare URLs with no title or image in Google Messages chats. A preview … |
| [Slackbot](https://www.pathwren.workers.dev/crawler/slackbot.html) | `Slackbot` | Slack | Slack stops being able to read your robots.txt, which is a strange thing to want. Block th… |
| [Slackbot-LinkExpanding](https://www.pathwren.workers.dev/crawler/slackbot-linkexpanding.html) | `Slackbot-LinkExpanding` | Slack | Your links appear in Slack as bare URLs. Inside working teams that quietly costs you click… |

[json](https://www.pathwren.workers.dev/category/preview.json)

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