SLF vs US ZipCode
Same instrument, two spec sheets — measured, not claimed.
SLF vs US ZipCode: common questions
Which is more reliable, SLF or US ZipCode?
On our scheduled checks, US ZipCode leads on measured uptime — SLF at —% versus US ZipCode at —% over 90 days. These are our own probe results, not provider claims; the uptime bars above show the day-by-day record for both.
Do SLF and US ZipCode need an API key?
SLF needs no key, while US ZipCode requires a free API key. If you want to start calling without signup, reach for SLF first.
Can I call SLF and US ZipCode from the browser?
Yes — both SLF and US ZipCode send CORS headers over HTTPS, so front-end code can fetch either directly with no backend proxy. That makes them easy to swap in a client-side app while you compare responses.
Are SLF and US ZipCode free for commercial use?
SLF has unclear commercial terms, and US ZipCode has unclear commercial terms. We track service terms and the data license as separate fields — see the Commercial use and Data license rows above, and confirm both before shipping either in a paid product.