What is the top free pick among iaC tools?

Pulumi leads the Stack Gems list for iaC tools. Verdict: IaC for developers who want real programming languages.

How many iaC tools does Stack Gems review?

4: 4 free or open source. Each review has a verdict and an honest Catch; no tool pays for its spot.

Which iaC tools have the most GitHub stars?

Terraform (50k), OpenTofu (30.6k), SST (26.4k), per GitHub on 2026-10-21. Stars measure attention, not fit; read the Catch.

What is the catch with Pulumi?

Smaller ecosystem than Terraform.

Best of · DevOps

Best iaC tools (2026)

Stack Gems reviews 4 iaC tools: 4 free or open source. These are the top 4, each with its verdict and the Catch we would want to know before installing it.

Order: free and open source first, then hosted products with a real free tier, then paid-led; catalog order inside each group, with quiet or archived repos last. Not a score, and no tool pays for its place.

4 reviewed · 4 shown in full

1.PulumiInfrastructure as code in real languages
Free / OSS · Freemium · 25.8k GitHub stars
VerdictIaC for developers who want real programming languages.
CatchSmaller ecosystem than Terraform. Learning curve for infrastructure patterns. The state service is a dependency unless self-hosted.
2.SSTMIT infrastructure-as-code for AWS, with live Lambda dev
Free / OSS · OSS/MIT · 26.4k GitHub stars
VerdictMIT IaC for AWS. Live dev is the feature; the bill is still Amazon.
CatchAWS-shaped. Other clouds are not the happy path. You still pay AWS. The Ion/v3 cut left a trail of outdated v2 tutorials — read current sst.dev docs.
3.OpenTofuMPL-2.0 Linux Foundation Terraform fork; truly OSS IaC
Free / OSS · MPL-2.0 · 30.6k GitHub stars
VerdictMPL-2.0 Terraform-compatible IaC. The OSS license answer to BSL.
CatchVs Terraform/Pulumi: license-first fork of Terraform 1.5-era lineage — not Pulumi programming-language IaC. Not HashiCorp Cloud/Enterprise features. Provider edge cases exist; verify before big migrations.
4.TerraformHashiCorp's infrastructure-as-code CLI; BUSL-1.1 source-available, free to self-host
Free / OSS · Source-available (BUSL-1.1) · 50k GitHub stars
VerdictThe default IaC tool; fine to self-host, and OpenTofu is there if you need open source.
CatchTerraform is under BUSL-1.1 (Business Source License): free to use and self-host, including in production, but you can't offer it as a competing paid hosted or embedded service. Each version becomes MPL-2.0 four years after release. OpenTofu is the MPL-2.0 fork. GitHub shows the license as NOASSERTION because BUSL is not an OSI license; the LICENSE file is the one to read.

FAQ

What is the top free pick among iaC tools?: Pulumi leads the Stack Gems list for iaC tools. Verdict: IaC for developers who want real programming languages.
How many iaC tools does Stack Gems review?: 4: 4 free or open source. Each review has a verdict and an honest Catch; no tool pays for its spot.
Which iaC tools can I self-host for free?: SST, OpenTofu and Terraform.
Which iaC tools have the most GitHub stars?: Terraform (50k), OpenTofu (30.6k), SST (26.4k), per GitHub on 2026-10-21. Stars measure attention, not fit; read the Catch.
What is the catch with Pulumi?: Smaller ecosystem than Terraform.

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