Every resource on the web has a URL. How that URL is constructed affects caching, routing, SEO, and the ease of migrating data between systems. UUIDs (Universally Unique Identifiers) are one way to generate the unique portion of a URL or database record identifier, but they are not the right choice in every situation. Understanding when to use them and when to use alternatives is a practical skill for anyone building web applications. This piece covers the UUID specification, when UUIDs belong in URLs, when they do not, and what the alternatives look like. What a UUID Is A UUID is a 128-bit identifier, typically rendered as a 36-character string in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx . The most common version in web development is UUID v4, which is generated from random or pseudo-random data. The standard is defined in RFC 4122 . The collision probability for UUID v4 is astronomically low. Generating a duplicate requires creating approximately 2.71 quintillion UUIDs.…