The Linespider crawler
LINE uses Linespider/1.1 to fetch pages for link previews. The full user agent:
Linespider/1.1 (+https://lin.ee/4dwXkTH)
It runs server-side and does not execute JavaScript.
20MB download limit
Linespider downloads up to 20MB of page content – far more generous than most preview crawlers (Slack reads only the first 32KB). Even large HTML pages get fully processed, though your meta tags should still be early in the <head>.
robots.txt behavior
Linespider respects robots.txt:
User-agent: Linespider
Allow: /
Blocking it prevents LINE from generating link previews.
No JavaScript execution
Client-side rendered meta tags won’t be seen. OG tags must be in the initial HTML response.
Response requirements
Expects 200 OK with text/html. Redirects are followed. Auth-protected or IP-restricted pages won’t generate previews.
Checking if Linespider can reach your page
curl -A "Linespider/1.1" https://example.com/your-pageIf your <meta> tags are in the response, LINE will generate a preview.