/config /terraform/variable-precedence-tfvars

Terraform variable precedence: tfvars, auto.tfvars, -var and TF_VAR_

updated 2026-10-20

tool: Terraform
file: terraform.tfvars / *.auto.tfvars / *.tfvars
key: variable values
type: HCL assignments: name = value
default: the variable's default

A root module variable can get its value from several places. Terraform loads them in a fixed order and the last one wins: the default in the variable block, then TF_VAR_name environment variables, terraform.tfvars, terraform.tfvars.json, *.auto.tfvars files in alphabetical order, and finally -var-file and -var options in the order they appear on the command line.

See the order

bash

cat > main.tf <<'EOF'
variable "env" {
  type    = string
  default = "from-default"
}
output "env" {
  value = var.env
}
EOF
terraform init -input=false -no-color >/dev/null
show() { terraform plan -no-color -input=false "$@" | grep '+ env'; }
show
TF_VAR_env=from-env-var show
echo 'env = "from-terraform.tfvars"' > terraform.tfvars
TF_VAR_env=from-env-var show
echo 'env = "from-auto.tfvars"' > prod.auto.tfvars
show
echo 'env = "from-var-file"' > ci.tfvars
show -var-file=ci.tfvars
show -var-file=ci.tfvars -var env=from-cli

Output

  + env = "from-default"
  + env = "from-env-var"
  + env = "from-terraform.tfvars"
  + env = "from-auto.tfvars"
  + env = "from-var-file"
  + env = "from-cli"

TF_VAR_env loses to terraform.tfvars, which loses to *.auto.tfvars, which loses to explicit -var-file and -var.

Order, first to last

#	Source	Loaded
1	default in the variable block	always
2	TF_VAR_name environment variables	always
3	terraform.tfvars	automatically, if present
4	terraform.tfvars.json	automatically, if present
5	.auto.tfvars, .auto.tfvars.json	automatically, in alphabetical order
6	-var-file=FILE and -var name=value	in command-line order

Sources

errors · terraformTerraform: Reference to undeclared input variableterraform validate and plan fail with Reference to undeclared input variable when code uses var.name without a variable block in the same module. How to fix it.flags · terraformterraform plan -out: save a plan and apply exactly that planterraform plan -out=tfplan saves the plan to a file; terraform apply tfplan then applies exactly those changes without a prompt. Inspect it with terraform show.cheat sheets · terraformTerraform cheat sheet: init, plan, apply, state and workspacesTerraform cheat sheet: init and upgrade, fmt and validate, plan and apply, outputs, state list, mv and rm, import, workspaces, and common language syntax.

See the order

Order, first to last

Sources

Related pages