Comparison · updated 2026-05-17

Synthorai vs OpenRouter

Two LLM API gateways, both with BYOK + Stripe + cross-provider routing. OpenRouter has wider model selection. Synthorai goes deeper on billing correctness and team management. Here's the honest breakdown.

TL;DR

• Pick OpenRouter if you want the largest model catalogue (300+ including obscure providers) and care most about free-tier models for prototyping.
• Pick Synthorai if you have a team / multi-tenant setup, want explicit BYOK key vault with per-model whitelisting, and want to read the actual billing-correctness implementation before trusting your quota to it.
• Use both — they don't conflict. OpenRouter as your experimentation playground, Synthorai for production usage where per-team quota + audit trail matter.

Feature-by-feature

Where Synthorai genuinely wins

• Crash-safe billing — the inflight ZSET pattern we use prevents quota leakage when a request dies mid-flight. We've written up the full implementation in Crash-Safe Billing for LLM Gateways. OpenRouter has its own correctness story but doesn't document it publicly.
• Workspace-level BYOK with model whitelist — each workspace's owner sets vault keys, can scope them to specific models (model_filter column), and can toggle always_use=1 to disable platform-key fallback. Useful when a customer says "for our compliance, never use your platform OpenAI key — only ours". See BYOK Pricing Invariants.
• Cross-provider prompt cache translation — Anthropic uses cache_control blocks, OpenAI auto-caches, Gemini has implicit caching. We've worked out the translation matrix; some translations are lossy (documented). Prompt Caching Across Providers walks through what translates and what doesn't.
• Raw upstream usage JSON in audit log — every billing_logs row stores the upstream provider's raw usage object. Useful when reconciling a customer's bill against the provider's own billing dashboard.

Where OpenRouter genuinely wins

• Model breadth — they integrate ~6× more models, including a lot of long-tail providers (Mistral fine-tunes, Cohere, DeepInfra-hosted open-weight models, etc.). If you're searching for "the cheapest Llama 3.3 70B endpoint right now", they have it and we don't.
• Free tier — they offer selected free models with rate limits, useful for prototyping. Synthorai is pay-as-you-go from day one (you can fund $1 to try, but no truly free tier).
• Brand recognition — they're a year older and have a large public Discord. If you ask on r/LocalLLaMA "which LLM gateway should I use", you'll get OpenRouter as the default answer.

Migration steps (OpenRouter → Synthorai)

1. Sign up + top up. Use the $50 launch promo for an extra 10% off all models for 30 days while you evaluate.
2. Swap base URL. Our endpoint is OpenAI-compatible. Most OpenRouter clients work by changing one env var:

   OPENAI_BASE_URL=https://synthorai.io/v1
   OPENAI_API_KEY=sk-syn-...

3. (Optional) Move BYOK keys. If you BYOK'd to OpenRouter, you can re-add the same keys in Synthorai's Vault. Per provider, one key. The BYOK billing invariants post covers what we charge on top (typically 0%).
4. Move workspace structure. If you used OpenRouter's API keys to segment teams, recreate as Synthorai workspaces with per-key quota.
5. Test for a week, keep OR as failover. Set up two base URLs in your SDK; route 90/10 first, then 100%. No lock-in either way.

Pricing

Both gateways are usage-based. Differences:

• Synthorai — you fund a wallet via Stripe, requests decrement it at provider list price. BYOK requests bypass the wallet (you pay the provider directly; we collect 0% surcharge currently). No markup on list price. See full pricing.
• OpenRouter — you fund credits, they apply a small markup on each provider's list price. BYOK requests bypass credits.

Net cost difference for non-BYOK usage is small (single-digit %). For BYOK-heavy usage, both end up roughly equivalent.

Comparison written 2026-05-17. OpenRouter feature parity may change; if anything here is out of date, email support@synthorai.io and we'll update.