IaC Bazaar vs Terragrunt
Open-source orchestration wrapper · Terragrunt site
The de-facto open-source wrapper for keeping Terraform and OpenTofu DRY across many environments.
Same layer - a real alternative
This is the comparison Vizier exists for, so it is worth being plain about it. Terragrunt and Vizier do the same job: DRY, dependency-ordered runs across many environments. They are alternatives, not complements, and most teams will pick one. Terragrunt is free and open source and has been the answer for years; Vizier adds a check on what a module IS before it runs, and hands you a receipt saying what was admitted.
What Terragrunt is
A thin, open-source (MIT) wrapper around the Terraform/OpenTofu binary, maintained by Gruntwork. A terragrunt.hcl per unit composes shared configuration through include, generates the backend and provider blocks so they are not copied into every environment, wires inputs between units through dependency blocks, and runs a whole tree in dependency order. It orchestrates whatever you point it at: what a module IS, and whether anybody has ever run it, are not questions it asks.
Pricing
Free and open source. Gruntwork separately sells the IaC Library and support subscriptions, which are a different product - see /compare/gruntwork.
Coverage
Cloud-agnostic. It wraps the engine, so it works wherever Terraform or OpenTofu works.
Where IaC Bazaar wins
- Vizier checks the MODULE before it runs, not just the plan. Each source is resolved against a catalog of live-tested, cosign-signed modules and refused if it cannot clear the evidence floor you set - fail-closed by default. Terragrunt has no notion of module provenance: an unsigned module from a fork of a fork applies exactly like a reviewed one.
- The check is only worth the catalog behind it. Anybody can add a signature check to a wrapper in an afternoon; what takes years is 183 modules that have actually been applied and destroyed in real accounts, with the evidence published.
- A receipt that leaves the building. A Vizier run produces a portable record of which modules were admitted, on what evidence and against which policy, which is the artifact an auditor asks for. Terragrunt produces terminal output.
- Vizier Central adds review before apply, roles and durable history against your own Postgres, with the maker-checker rules enforced in the database rather than in a client. Terragrunt is a CLI and leaves that to whatever CI you bolt around it.
Where Terragrunt leads
- Free and genuinely open source, MIT-licensed, with no vendor in the path. Vizier is proprietary and distributed as a binary, and for a lot of teams that difference settles it on its own.
- Adoption and maturity. It is the answer people already have, with years of accumulated edge cases handled, an enormous body of public examples, and an answer on Stack Overflow for most things that go wrong.
- A richer configuration language for composition: generate blocks, before/after/error hooks, mock outputs for planning against unapplied dependencies, and fine-grained control over what gets included from where.
- It does not care where your modules come from, which is a feature when your modules are internal, unpublished, and never going to appear in anybody catalog.
- No catalog dependency and nothing to subscribe to. If a proof check is not something your organisation is asking for, it is overhead you are not obliged to carry.
The honest take
Terragrunt and Vizier solve the same first problem - DRY, dependency-ordered runs across many environments - and disagree about the second. Terragrunt runs any module you point it at and checks the plan. Vizier checks the module first: it resolves each source against a catalog of live-tested, signed modules and refuses what cannot clear your bar, then produces a receipt saying so. If the modules you run are internal and unpublished, Terragrunt is the more direct fit and it is free. If you are consuming third-party modules and need to show somebody what was admitted and why, that is the gap Vizier is built for.
Fact-checked against Terragrunt's own pages (terragrunt.gruntwork.io, terragrunt.gruntwork.io, github.com). Corrections welcome via contact.