1. Use Basic mode through any of these means (see [mw:Compatibility](https://www.mediawiki.org/wiki/Compatibility#Browsers) or [wikitech:Frontend practices](https://wikitech.wikimedia.org/wiki/MediaWiki_Engineering/Guides/Frontend_performance_practices#Getting_started)):
** Use any Chrome 49-62 or Firefox 49-57 version, e.g. via BrowserStack (+BrowserStackTunnel, as their datacenter IP will be blocked)
** Use a modern browser with a slow or spotty connection where `load.php?modules=startup` times out, has a syntax error, or is sufficiently slow that you submit your edit before it arrives (e.g. block one request in DevTools)
** Use Tor in safe mode from an IP-exempt account.
2. Open https://en.wikipedia.org/w/index.php?title=Wikipedia:Sandbox&action=edit
3. Without changing anything, submit it as a no-op.
**Actual**
Firefox 57 (default settings, nothing disabled or changed)
```counterexample
Incorrect or missing CAPTCHA.
```
{F74857144 height=300}
Firefox 147 (simluate startup.js fail/timeout)
```counterexample
Incorrect or missing CAPTCHA.
```
{F74857836 height=300}
**Other information**
>>! https://www.mediawiki.org/wiki/Compatibility policy:
> Grade C browsers must receive the core functionality of the MediaWiki platform. […] this means content is presented in a readable manner, and all page and account actions are discoverable and work.
In theory the captcha requirement should not apply to non-new accounts (which have the skipcaptcha right). However, due to T422219 these users currently can't login.