Onlinesim

Virtual numbers for private registration

APICapable readiness

About

What is Onlinesim

Onlinesim lets you order virtual phone numbers, receive SMS messages on them, and copy out confirmation codes — all without a physical SIM. It's built for founders and GTM engineers who need to register accounts at scale, verify services programmatically, or keep personal numbers out of third-party platforms. The standout capability is per-client number allocation with re-receipt support, meaning the same number can receive multiple messages rather than expiring after a single use. Numbers can be rented for as little as 20–40 minutes from $0.01, or held for days at a time starting at $3/day. The main limitation is narrow integration depth — Dolphin Anty is the only named integration, so teams expecting native CRM or workflow connectors will need to build those bridges themselves via the API.

Utility Data & Discovery

Capabilities

Key features

Phone verification

confirms a number is live and mobile-capable

Outbound webhooks

event-driven integrations

Our verdict

Vanderbuild take

For founders and GTM engineers who need phone verification at volume without burning real SIM cards, Onlinesim is a straightforward utility that does exactly what it says. The REST API is documented and accessible, so you can wrap number provisioning and SMS polling into your own automation stack or MCP layer without much friction — agentic readiness here is real, not theoretical. Pricing starts at $0.01 per activation and $3/day for rentals, which is affordable for small teams testing workflows, though costs can accumulate quickly if you're running high-frequency account registration pipelines. The honest limitation is that the integration surface is thin — Dolphin Anty is the only named partner, and there's no evidence of webhook push delivery, meaning you'll need to poll the API for incoming messages rather than receiving event-driven callbacks.

Mateusz Sekta

Founder, vanderbuild

The wedge

Agentic stack profile

API

REST

Programmatic access available.

REST API — straightforward to call from any agent or workflow tool. Rate limits and auth vary by plan.

API docs →

Agentic readiness

Capable

Solid API access — wraps cleanly for agent use.

Solid REST or SDK access. No MCP server yet, but easy to wrap in custom agent tooling. Most modern SaaS tools land here.

Stack role

Verifier

Where this tool slots into an agentic pipeline.

Plays the role of Verifier in an agentic pipeline. Use it to validate emails or phones before an agent sends or dials.

Compare

Onlinesim alternatives

Tools that solve a similar problem — compared at a glance.

Onlinesim(this tool)

Pricing: Freemium
Budget: $$
Best for: Founder, GTM Engineer

Readiness: Capable
API: REST

Smspva

Pricing: Freemium
Budget: $
Best for: Founder, GTM Engineer

Readiness: Capable
API: REST

Textverified

Pricing: Usage-based
Budget: $
Best for: GTM Engineer, Founder

Readiness: Capable
API: REST

Answers

Frequently asked questions

Does Onlinesim have a public API?

Yes — Onlinesim ships a REST API. Docs: https://onlinesim.io/openapi_docs/Onlinesim-API-UN/info.

How much does Onlinesim cost?

Onlinesim: pricing is freemium, expect mid tier ($$) spend. Full pricing page: https://onlinesim.io/price-list.

Who is Onlinesim best for?

Onlinesim is built for Founder, GTM Engineer. Fits SMB (1-50), Mid-market (50-500)-sized teams.

How well does Onlinesim fit an agentic sales stack?

Tier: Capable. Solid public API, no MCP yet — straightforward to wrap in your own agent tooling.

Quick spec

APIREST ↗

ReadinessCapable

Stack roleVerifier

Pricing

Freemium

Vendor pricing →

Ideal customer

Growth stage

Growth-stage · Scale-up

Company size

SMB (1-50) · Mid-market (50-500)

Best for

Founder · GTM Engineer