Development Mode allows you to temporarily suspend Cloudflare's edge caching and minification features. The expiration period for Development Mode is 3 hours.
You will find the Development Mode option by selecting the 'Caching' option from the top bar menu:
Development Mode will be found at the bottom of the page:
NOTE: Development Mode does not clear the edge cache for your site - it simply suspends the use of it while Development Mode is enabled. If you need to specifically clear the cache you should use the Single File Purge or Full Cache Purge functions.