The 10 Best LLM Routing and Load Balancing Tools in 2027

OpenRouter puts 600+ active models on 80+ providers behind one API. By default it routes each request on each provider’s measured price, throughput, latency and reliability, and you can override that with a sort by "price", "throughput" or "latency". Fallbacks are on by default, the models parameter tries backup models, and the Auto Router picks a model per prompt. The Standard plan carries a 5.5% platform fee.

LiteLLM gives one OpenAI-format interface to 100+ LLMs and a router with weighted pick (the default), rate-limit aware, latency-based, least-busy and lowest cost strategies. Fallbacks move to another model group after retries, with separate context window and content policy fallbacks. The code is MIT licensed outside its enterprise/ directory; Enterprise is custom pricing with a 30-day trial key.

Portkey’s gateway combines weighted load balancing, fallbacks and conditional routing on metadata or request parameters in one config. The open-source gateway is MIT licensed and routes to 1,600+ models. The Developer plan is free with 10k recorded logs per month and Production is $49/month. Portkey’s docs say it is now Prisma AIRS AI Gateway.

Vercel AI Gateway reaches 400+ models through one key and routes a model across healthy providers with ordered provider and model fallbacks, logging every attempt. Vercel says it charges no markup and no platform fee on tokens, including when you bring your own key, and you can set budgets per team, project, key or member.

Cloudflare AI Gateway builds dynamic routes from conditional, percentage, model, rate limit and budget limit nodes, so you can split traffic for A/B tests or send paid users to a different model and fall back when a quota runs out. Core features are free on all plans; a 5% fee applies to credits bought through Unified Billing. Dynamic routing is marked Beta.

Kong’s AI Proxy Advanced plugin has the widest set of balancing algorithms here: round-robin, consistent-hashing, least-connections, lowest-latency, lowest-usage, semantic and priority. It supports retries, timeouts and failover across mixed providers from v3.10. It is only available in the AI Gateway Enterprise offering, and no price is published on the plugin page.

Amazon Bedrock Intelligent Prompt Routing predicts the response quality of each model per request and routes within one family: Anthropic, Meta Llama or Amazon Nova. You pick a fallback model and a response quality difference that decides when to switch. AWS says it can reduce costs by up to 30%, but it is only optimized for English prompts.

Not Diamond predicts which model to use for each prompt, using pre-trained routers or custom ones trained on your data. It costs $0.05 per million tokens routed on pay-as-you-go and adds an average of 100-150ms per request. It says teams save at least 20-40%, and it is not a gateway: it plugs into the one you already run.

Helicone AI Gateway offers one OpenAI-compatible API for 100+ LLM providers with automatic failover and credits at 0% markup. Its self-hosted Rust gateway, under GPL-3.0, adds model-based latency routing and P2C + PeakEWMA provider routing, and its README lists P95 latency under 5ms.

RouteLLM, from LMSYS, routes each query between a strong and a weak model using a cost threshold, with mf, sw_ranking, bert, causal_llm and random routers. It runs as a drop-in OpenAI client or an OpenAI-compatible server under Apache-2.0, and reports cutting costs by up to 85% while keeping 95% GPT-4 performance on MT Bench.