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Docker Image Size Calculator

Estimate the real download size of an image, layer by layer, or analyze a Dockerfile for security and optimization issues — before docker pull or docker build.

  • layers
  • size
  • multi-arch
  • Dockerfile lint
Waiting to check...
image reference
The "Registry" check runs from the Backserver server, calling the Docker Registry HTTP API v2 directly (no Docker install needed); its numbers are the compressed, downloadable size, not the final on-disk size. Compatible public registries (Docker Hub, GHCR, Quay, GCR) are supported, and connections to internal addresses are blocked. The "Dockerfile analysis" section runs entirely in your browser; your file is never sent anywhere unless you explicitly click "Get base image size" for the final stage. This analysis is based on common Docker security and optimization rules, not a real build — the true final size can only be determined by running docker build.
ABOUT

Calculate Docker image layer sizes and lint your Dockerfile

A heavy image means slow pulls, slow deploys and a larger attack surface. This tool shows the size of every layer of an image on the registry (including multi-arch images) so you can see which layer dominates, and lints your Dockerfile for issues such as apt-get update split from install, uncleaned package caches, ADD used instead of COPY and running as root. The registry lookup runs server-side.

HOW TO

How to use it

  1. Enter the image with its tag, for example nginx:1.27-alpine.
  2. Review the layers and total size.
  3. Paste a Dockerfile into the analyser to get size-reduction suggestions.
FAQ

Frequently asked questions

How do I shrink an image?
Use a slim base (alpine or slim), multi-stage builds, and combine RUN instructions to reduce layers.
Why does the size differ from docker images?
This shows the compressed size of layers on the registry; docker images reports the unpacked size on disk.