Environment Variables

Mimic is configured entirely through environment variables. There is no configuration file — the mocks directory is the configuration, and everything about the server itself is set via env vars.

Server

Variable	Default	Description
PORT	8080	The TCP port Mimic listens on.
MIMIC_BIND_ADDRESS	0.0.0.0	Network interface to bind. Set to 127.0.0.1 to restrict access to localhost. Both IPv4 and IPv6 literals are accepted (e.g. ::1, ::) — don’t append a port. An unparsable value fails startup rather than silently falling back to 0.0.0.0. Inside Docker, leave this at 0.0.0.0 — 127.0.0.1 there means “this container”, not “this host”. See Binding Address below.
RUST_LOG	info	Log verbosity: trace, debug, info, warn, error.

Binding address

By default Mimic listens on every network interface, which is convenient on a laptop but means the mock server, its request log, and its admin API are reachable from anywhere that can route to the machine. On a shared box or a machine with a public IP, MIMIC_BIND_ADDRESS restricts it:

MIMIC_BIND_ADDRESS=127.0.0.1 mimic   # only this machine can reach it
MIMIC_BIND_ADDRESS=::1 mimic         # IPv6 loopback

The bound address is always visible — it’s printed in the startup log next to the port, and reported by GET /health as bind_address. See What the Request Log Keeps for what’s exposed if the admin API is reached.

Mocks

Variable	Default	Description
MIMIC_MOCKS_DIR	/app/mocks if it exists, else ./mocks	Directory (or single .json/.yaml/.yml file) mocks are read from. Used verbatim when set — a path that doesn’t exist is reported as missing rather than silently replaced.
MIMIC_MAX_BODY_SIZE	10485760 (10 MB)	Maximum request body Mimic will buffer, in bytes. Requests over the limit get 413 Payload Too Large.
MIMIC_MAX_RESPONSE_FILE	10485760 (10 MB)	Largest file a mock may serve with response_file, in bytes. 0 removes the cap.
MIMIC_STRICT_TRAILING_SLASH	false	Disable trailing-slash tolerance — /things and /things/ become distinct paths again.
MIMIC_HEAD_FROM_GET	true	Answer a HEAD from the mock the matching GET would have used. false = a HEAD is answered only by an explicit HEAD mock. See HEAD Requests.
MIMIC_STRICT_IGNORE_HEADERS	unset	Comma-separated header names to add to strict header mode’s built-in ignore list.

Health & Admin

Variable	Default	Description
MIMIC_HEALTH_PATH	/health	Where the health check is served. Empty disables it, freeing the path for a mock.
MIMIC_ADMIN_PREFIX	/admin	Prefix the admin API is mounted under.
MIMIC_DISABLE_ADMIN	false	Switch the admin API off entirely.
MIMIC_ADMIN_TOKEN	unset	Bearer token the admin API requires. Unset means no authentication.

See Reserved Endpoints for the exact routes these control, and Admin Dashboard for how the token is checked.

Request Log

Variable	Default	Description
MIMIC_MAX_LOG_ENTRIES	1000	How many requests the admin request log keeps. 0 is unbounded.
MIMIC_MAX_RECORDED_BODY	65536 (64 KB)	How much of each request/response body the log stores, in bytes. 0 stores whole bodies.
MIMIC_REDACT_BODY_FIELDS	password,token,secret,api_key (and variants — see below)	Body field names whose values are replaced with [REDACTED] in the request log, comma-separated. Empty stores bodies verbatim.
MIMIC_DISABLE_BODY_LOG	false	Store no request/response bodies in the log at all.

Full defaults and behavior in What the Request Log Keeps.

Scenario Tags

Variable	Default	Description
MIMIC_ACTIVE_TAGS	unset	Scenario tags active at startup, comma-separated. Unset means every mock is matchable regardless of tags.

See Scenario Tags.

CORS

Variable	Default	Description
MIMIC_CORS	false	Master switch. Everything below is ignored while it’s off.
MIMIC_CORS_ORIGINS	*	*, or a comma-separated allowlist.
MIMIC_CORS_METHODS	GET,POST,PUT,PATCH,DELETE,OPTIONS	Advertised as Access-Control-Allow-Methods on a preflight.
MIMIC_CORS_HEADERS	*	* reflects the request’s Access-Control-Request-Headers; a list is sent verbatim.
MIMIC_CORS_CREDENTIALS	false	Sends Access-Control-Allow-Credentials: true.
MIMIC_CORS_MAX_AGE	600	Access-Control-Max-Age, in seconds.

See Built-in CORS.

Proxy & Recording

Variable	Default	Description
MIMIC_PROXY_UPSTREAM	unset	Forward unmatched requests to this upstream instead of 404ing.
MIMIC_RECORD_UPSTREAM	false	Record proxied responses as new mock files.
MIMIC_PROXY_TIMEOUT_MS	5000	How long to wait for the upstream before falling back to a 404.
MIMIC_PROXY_BUFFER_LIMIT	10485760	Bytes of an upstream response buffered for the log and recording; larger or text/event-stream responses are streamed. 0 = always buffer.
MIMIC_RECORD_MATCH_HEADERS	unset	Extra request headers to pin as matchers on a recording, comma-separated.

See Proxy & Record-and-Replay.

Setting variables

docker run

Pass each variable with -e:

docker run -d \
  --name mimic \
  -p 8080:8080 \
  -e PORT=8080 \
  -e RUST_LOG=info \
  -v $(pwd)/mocks:/app/mocks:ro \
  ragilhadi/mimic:latest

docker-compose.yml

Use the environment block:

services:
  mimic:
    image: ragilhadi/mimic:latest
    environment:
      PORT: 8080
      RUST_LOG: info

.env file

Docker Compose automatically reads a .env file in the same directory as the compose file:

.env

PORT=8080
RUST_LOG=info

Reference the variables in your compose file with ${VAR}:

services:
  mimic:
    environment:
      - PORT=${PORT}
      - RUST_LOG=${RUST_LOG}
    ports:
      - "${PORT}:${PORT}"

Running from source

If you’re running a locally built binary instead of the Docker image, export the variables in your shell:

export PORT=8080
export RUST_LOG=debug
cargo run --release