from Hacker News

https://unpkg.com/ appears to be experiencing some instability and unreliability right now. This is an <excellent> opportunity to identify any assets that you're not caching and/or are directly pulling from unpkg.com in your production environment.

I've encountered "HTTP 520 Web server is returning an unknown error" responses intermittently from Cloudflare.

Recurring downtime for unpkg.com has been an issue in the past. In August 2022, Shopify notified its partners to switch from unpkg.com to jsdelivr.net [1]. I can only speculate that Shopify made this recommendation due to the negative impact of unpkg.com's downtime on numerous online shops.

[1]: jsdelivr.net offers a convenient tool for this migration at https://www.jsdelivr.com/unpkg.