Modern open networking, in your development environment
The mobile networks most developers grew up with were closed, opaque, and built for human SIMs. SIMSY is built differently. We run a virtualised, cloud-native mobile core — the way Amazon and Azure built compute and storage — so cellular becomes another primitive you can program against.
SIMSY Developers is a hands-on portal of tools, recipes, and reference projects that change the way mobile networks get used. Drop in a SIM, hit an API, ship.
Cellular as a cloud primitive
Mobile networks have always been the missing primitive in modern infrastructure. CPU, memory, storage, and HTTP are programmable; the SIM was a shipping label. We changed that. With SIMSY you compose mobile network features the way you compose S3 buckets or Cloudflare Workers.
API-first
Every part of the network — SIMs, routing, policies, identities, events — is exposed through a clean HTTP API. No portal-only features.
Identity as authentication
Every SIM has a network identity. The Edge API recognises the calling SIM session and returns scoped data. No tokens to rotate, no secrets on the device.
Cloud-native mobile core
A fully virtualised core network. We control the routing layer, so we can do things at the SIM that used to require a rack of CPE.
Programmable everything
Multi-APN per SIM, network-level data redirection, private LAN between SIMs, URL-locking, network-native telemetry. Compose primitives, ship features.
Five ways to use the network today
Each of these is a reference implementation built on top of the SIMSY platform. Use them as-is, or read the source and build your own.
Cellular Private LAN
Put two or more SIMs in the same private subnet via a shared VSlice. Direct SIM-to-SIM networking, default-deny external, no VPN, no fixed IPs, no tunnels.
Remote Access Proxy
Drop your API token into the proxy app and reach any service over your SIMSY connection from anywhere — no port forwarding, no inbound holes.
Android Router
Turn a spare Android phone into a SIMSY-managed router in minutes. Cellular backhaul, network policies, full management — no extra hardware.
USB Host
Give your local AI agent a private cellular tunnel via a £20 USB modem. Combine with Cellular Private LAN or the Proxy app for secure remote access.
Pi Hat + Cloudflare
Teltonika Pi Hat + SIMSY SIM + Cloudflare Tunnel. Remote-accessible Raspberry Pi, anywhere there is cellular, with full SSO.
One REST surface, one Bearer token
Every part of the network — endpoints, VSlices, routing, events, diagnostics — is on the same fully-OpenAPI-documented REST surface at api.s-imsy.com/api/v1. Generate a token in the portal, paste it in the Authorization header, you are off.
148 endpoints. OpenAPI 3.0.1. Interactive docs you can hit "Try it out" on. No proprietary SDK required.
See the full quickstart$ export SIMSY_TOKEN="eyJhbGciOiJI..." # JWT from the portal
$ curl https://api.s-imsy.com/api/v1/endpoints \
-H "Authorization: Bearer $SIMSY_TOKEN"
# Each endpoint returns its identifiers, group, VSlice,
# routing policy, latest country and operator, current
# IP address, and rolling usage. Everything else hangs
# off /api/v1/endpoints/{id}/...Get a developer SIM and start building
Email us with what you're working on and we'll send a SIM with credit so you can try every tool on this page.