Building a telco, in public.
Technical guides from the engineers building Firsty.
eSIM API comparison: Firsty vs Twilio vs Telnyx for builders
A developer-focused comparison of eSIM APIs — routing, pricing, provisioning latency, and integration effort — covering Firsty, Twilio Super SIM, and Telnyx.
Firsty vs Twilio: choosing a connectivity API for global apps
A practical comparison of Firsty and Twilio for builders embedding cellular connectivity, eSIM, and IoT data into their products.
Data Roaming Optimization for eSIM Applications
How data roaming works under the hood, why carrier switching adds latency, and how to optimize both through API design. A technical guide for engineers building global eSIM products.
How to Become an eSIM Reseller in 2026: Step-by-Step Guide
A practical guide to becoming an eSIM reseller. What it costs, what margins to expect, the 4 business models compared, and how to launch your first branded eSIM store in 2026.
How to provision your first eSIM via API in 30 minutes
From OAuth token to first eSIM activated, with QR code generation server-side. Real code, real credentials, real eSIM, in about 30 minutes.
OAuth2 client credentials in production: what most tutorials get wrong
Token caching, refresh strategy, and the security mistakes we see in production integrations every week.
How Pexx built a white-label travel eSIM product on top of the Firsty API
A case study on how the cryptowallet Pexx integrated the Firsty API to launch loyalty-driven free data for their users in under three months.
The LPA activation code format explained
What the LPA format actually is, how to render QR codes from it correctly, and why some QR codes work on iPhone but not Android.