DeepEval vs Promptfoo vs Braintrust in 2026 - The Eval Tool Showdown

DeepEval, Promptfoo and Braintrust all evaluate LLM apps, but they barely resemble each other in practice. One is a Python test framework, one is a YAML-driven security CLI, and one is a hosted regression platform. Pick by philosophy, not by feature list, and the right answer usually falls out fast.

DeepEval is pytest for LLM apps. Promptfoo is config-driven red-teaming. Braintrust is the turnkey regression platform. Here is the honest three-way breakdown.

The short version

	DeepEval	Promptfoo	Braintrust
Shape	pytest-style OSS framework	YAML-driven OSS CLI	Hosted eval platform
Free path	Apache-2.0, free forever	MIT, free forever	$0 Starter, then $249/mo
Signature strength	Research-backed metrics	Red-teaming, OWASP mapping	CI regression gates
Ownership	Independent YC startup	OpenAI company since 2026	Independent, Iconiq-backed
Best for	Python teams who test	Security and CI teams	Turnkey regression testing

DeepEval: pytest for LLM apps

DeepEval brings the pytest mental model to LLM evaluation. You use assert_test, you can mark tests with @pytest.mark, and you run the whole thing with deepeval test run - it drops into an existing Python test suite and CI pipeline like it belongs there. Under that runner sits 50+ research-backed metrics, including the widely-cited G-Eval, plus hallucination, answer relevancy, faithfulness, and RAG and agent metrics. The OSS framework is Apache-2.0 and fully usable with zero Confident AI account - the free build is a real, standalone product. It is also an independent YC startup, not owned by a model vendor.

The gotcha comes from its design - nearly all the metrics are LLM-as-judge. Every test case fires another LLM inference, so a big suite compounds into significant API bills, and runs take minutes not seconds, so CI needs explicit timeouts. If you move to the Confident AI cloud, watch the cliff - the Free tier is stingy at 5 test runs per week, and Starter at $200/mo jumps 10x to Team at $2,000/mo with nothing in between.

Promptfoo: YAML config plus serious red-teaming

Promptfoo is the open-source CLI for two jobs - evaluating LLM apps and red-teaming them for security. It is config-driven, not SDK-first - your evals are declarative YAML that lives in version control next to your prompts, which security and CI teams love because a reviewer reads them in a pull request. It is MIT-licensed with roughly 23.5k GitHub stars, the most of the major eval tools.

Red-teaming is the signature specialty. It ships 50+ attack plugins and built-in presets for the OWASP LLM Top 10, plus OWASP Agentic and NIST, probing for PII leakage, prompt injection, jailbreaks and more. The Community edition is MIT-licensed and free forever, with all core eval and red-teaming included - the only hard limit is 10k red-team probes per month. It also acts as its own OTLP receiver with a built-in trace viewer, so you do not need to stand up Jaeger or Tempo.

Two things to weigh. OpenAI acquired Promptfoo on 9 March 2026 - it stays open source under MIT and folds into OpenAI Frontier, but long-term governance under a single large owner is a fair question. And a GitHub issue (#7333) reports some agent-SDK providers do not export traces to the receiver, so verify your stack works before you rely on it.

Braintrust: the turnkey regression platform

Braintrust started with evals and built observability around them. Human review, automated scorers, LLM-as-judge, tracing, dataset management and CI/CD quality gates all share one system. The autoevals library ships working scorers out of the box, and the CI gates can block a merge on a statistically significant regression - actually stopping the bad code, not just logging it. There is no per-seat charge, so users are unlimited on every tier. It is well-funded too, with an $80M Series B from Iconiq in February 2026.

The gotcha is the billing meter. Braintrust bills “processed data” in GB, counting every byte of inputs, outputs, prompts and metadata, with no hard spending cap. Verbose multi-step agents and big RAG contexts burn the allowance fastest. The $0 Starter jumps straight to $249/mo Pro with nothing in between. Set billing alerts on day one. And self-host is hybrid-VPC only and Enterprise-only, with the Brainstore backend closed.

Which should you pick?

• Your team writes Python and thinks in tests - DeepEval. It is the most natural eval framework for a CI/CD workflow, and the OSS core is free and genuinely capable. Cost-model the LLM-judge calls before you scale the suite.
• Red-teaming or security testing is part of your eval work - Promptfoo. Nothing else in the open-source category has this complete an OWASP mapping, and the free tier is the real product.
• You want turnkey regression testing and CI gates without building the orchestration - Braintrust, with billing alerts on from day one.
• Budget is the deciding factor - Promptfoo or DeepEval, both of which let you run the real thing free. Braintrust’s real product starts at $249/mo.
• Vendor independence matters most - DeepEval’s Confident AI is an independent YC startup. Promptfoo is now an OpenAI company, which is the thing to weigh there.
• You want your evals in version control as declarative config - Promptfoo’s YAML-in-git shape fits that exactly.

These three are not really competing for the same seat. DeepEval owns the Python-test workflow, Promptfoo owns security red-teaming, and Braintrust owns turnkey regression gates. The good news is you can run DeepEval and Promptfoo side by side for free and only reach for Braintrust’s paid platform when a unified regression system earns its keep. Prices here come from each vendor’s own pages, verified for this category which ships breaking changes monthly.