The phrases writ large and at large are commonly confused. Here is a mnemonic for remembering the difference:
Writ large usually means clear or obvious. At large usually means in general.
The next section goes through dictionary definitions of the two phrases. If you prefer to learn by example, see the definitions of writ large and at large in the New Oxford American Dictionary.
Why should you believe some random internet guy about the difference between these two phrases? You don’t have to. You can believe dictionary editors, instead.
Webster’s New World College Dictionary
This is the dictionary of “first reference for spelling, style, usage and foreign geographic names” for the Associated Press Stylebook. Since I’m a journalist, and I’m targeting journalists with this information, I’ll use this as a first reference.
Below are the relevant definitions from Webster’s. Note that the links below are accessible only with a digital subscription to the dictionary via the AP Stylebook.
Note that the definition of writ large is from the entry on writ, which is an archaic preterite and past participle of write.
The definition of at large is from the entry on large.
New Oxford American Dictionary
The Oxford University Press publishes this dictionary, which also comes on Macs. The versions of these definitions are from Lexico.com, which hosts a free version of the dictionary.
Click the links with each definition to see extensive lists of example sentences for each phrase.