What is Docker Buildx? | DevOps Dictionary

Docker Buildx — Advanced Building With Multi-Platform Support

What Is Docker Buildx in Simple Terms?

Buildx is the advanced Docker build tool that exposes all BuildKit features through the CLI. The most useful feature is multi-platform building — you can build an image for both x86 (Intel/AMD) and ARM64 (Apple M1/M2, AWS Graviton) from a single command on a single machine, and Docker publishes a manifest that automatically serves the right architecture to each platform.

Bash

# Regular docker build — one platform
docker build -t payment-api:v3.1.0 .
# Builds for your current machine's architecture only
 
# Docker buildx — multiple platforms
docker buildx build \
  --platform linux/amd64,linux/arm64 \
  -t registry.razorpay.in/payment-api:v3.1.0 \
  --push .
# Builds for both architectures
# Pushes a manifest list that serves the right image per platform
# AWS Graviton instances automatically get the arm64 image
# Standard x86 servers automatically get the amd64 image

Setting Up Buildx

Bash

# buildx is included with Docker Desktop and Docker Engine 20.10+
docker buildx version
# github.com/docker/buildx v0.12.0
 
# Create a new builder (for multi-platform support)
docker buildx create \
  --name multiarch-builder \
  --driver docker-container \
  --use
 
# Inspect the builder
docker buildx inspect --bootstrap
# Shows: supported platforms: linux/amd64, linux/arm64, linux/arm/v7...
 
# List all builders
docker buildx ls
 
# Use a specific builder
docker buildx use multiarch-builder

Multi-Platform Build in GitHub Actions

YAML

* name: Set up QEMU (for cross-platform emulation)
  uses: docker/setup-qemu-action@v3
 
* name: Set up Docker Buildx
  uses: docker/setup-buildx-action@v3
 
* name: Build and push multi-platform
  uses: docker/build-push-action@v5
  with:
    platforms: linux/amd64,linux/arm64
    push: true
    tags: registry.razorpay.in/payment-api:v3.1.0
    cache-from: type=gha
    cache-to: type=gha,mode=max

BuildKit Features Through Buildx

Bash

# Secret mounts
docker buildx build \
  --secret id=github_token,src=$HOME/.secrets/github-token \
  -t myapp:latest .
 
# SSH mounts for private repos
docker buildx build \
  --ssh default=$SSH_AUTH_SOCK \
  -t myapp:latest .
 
# Registry cache export
docker buildx build \
  --cache-from type=registry,ref=registry.razorpay.in/payment-api:cache \
  --cache-to type=registry,ref=registry.razorpay.in/payment-api:cache,mode=max \
  -t registry.razorpay.in/payment-api:v3.1.0 \
  --push .
 
# Bake — build multiple images in parallel from a config file
docker buildx bake
# Uses docker-bake.hcl or docker-compose.yml to define build targets

PLACEMENT PRO TIP
**Tip:** Always use `docker buildx build` in CI/CD pipelines instead of `docker build`. Buildx gives you better cache support (cache-from/cache-to with registry), multi-platform capability when needed, and all BuildKit features like secret mounts. The commands are nearly identical — just add `buildx` after `docker`.