One API key for hundreds of AI models from every major provider
#1Respan: Open-source request routing with built-in evaluations, but has a smaller community and fewer pre-built provider connectors. LiteLLM records 576,967 monthly visits with +7.9% month-over-month growth and Freemium, Contact for Pricing pricing. Respan records 91,503 monthly visits with -14.5% growth and Freemium pricing.

Open-source AI gateway with observability and evals built in
| Dimension / Metric | ![]() | ![]() |
|---|---|---|
| Official Domain | litellm.ai | respan.ai |
| Pricing Model | Freemium, Contact for Pricing | Freemium |
| Monthly Visits | 576.97K (576,967) | 91.5K (91,503) |
| MoM Traffic Delta |
| +42.48K (+7.9%) |
| -15.53K (-14.5%) |
| Primary Market & Share | 🇺🇸 United States (27.9%) | 🇺🇸 United States (28.8%) |
|---|
| Direct Visits / mo | 228.97K | 23.12K |
|---|
| User Rating | 4.8 | 4.5 |
|---|
| Supported Platforms | Website | Website |
|---|

One open-source AI gateway for 100+ LLM providers
Call 100+ providers and 1,800+ models using one request format, so you can swap models without changing application code.
Issue scoped keys per team, project or app, set monthly spend caps and see exactly who is driving usage and cost.
Distribute traffic across deployments, retry on failure and automatically fall back to another model or provider when one goes down.
Dashboards for request volume, tokens and cost per model, with support for logging and analytics integrations.

Open-source AI gateway with observability and evals built in
Route to OpenAI, Anthropic, Google, xAI, DeepSeek, Qwen and many other models through a single API key and one OpenAI-compatible endpoint.
Keep your existing OpenAI, Anthropic, LangChain or Vercel AI SDK code and change only the base URL.
Automatic fallbacks, retries and load balancing across providers and API keys keep requests answering when a single provider rate-limits or fails.
Every call is logged and traceable, with evaluation tooling and a CLI so you can query logs and traces from your terminal.
One API key for hundreds of AI models from every major provider
#1
SpecialistHosts high-performance open-weight models directly on dedicated serverless infrastructure, but does not route across external providers.
#2One OpenAI-compatible gateway for adaptive LLM routing, guardrails, and spend control

Unified LLM gateway with failover and analytics, but offers less robust open-source developer SDK support.
AI gateway, observability and guardrails for production LLM apps

Provides managed multi-provider AI routing and cost tracking, but lacks the native open-source flexibility of LiteLLM.
Free / Open-sourceOne OpenAI-compatible API to route, monitor and control 250+ LLM models

Free / Open-sourceEvaluate, monitor, and govern your AI applications in production

One API key for 70+ AI models, 1,000+ data APIs and web tools
Free / Open-sourceOpen-source LLM observability and AI gateway for shipping reliable AI apps

Free / Open-sourceThe open-source LLM gateway that fixes your agents' requests on the fly

Free / Open-sourceAgent observability, evals and governance for AI platform teams
SpecialistHosts high-performance open-weight models directly on dedicated serverless infrastructure, but does not route across external providers.
One OpenAI-compatible gateway for adaptive LLM routing, guardrails, and spend control
Unified LLM gateway with failover and analytics, but offers less robust open-source developer SDK support.
Free / Open-sourceOne OpenAI-compatible API to route, monitor and control 250+ LLM models
Free / Open-sourceEvaluate, monitor, and govern your AI applications in production
Free / Open-sourceOpen-source LLM observability and AI gateway for shipping reliable AI apps
Free / Open-sourceThe open-source LLM gateway that fixes your agents' requests on the fly
Free / Open-sourceAgent observability, evals and governance for AI platform teams