While they sound similar, a 'Username Search' tool and a 'Username Availability Checker' serve different technical purposes and encounter different limitations.
1. What a Username Search Tests
A username search checks whether a publicly accessible profile exists right now at a given URL (e.g. returns HTTP 200).
Its goal is public footprint discovery and online presence mapping.
2. What Availability Checking Involves
Availability checking determines whether a new registration form will accept the handle.
A name might show as 'Not Found' on a public URL because it is suspended, shadowbanned, or reserved by the platform, yet still be unavailable for registration.
Summary Key Takeaway:
Always distinguish between public existence and registration eligibility when planning brand claims or investigating accounts.