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+# Dockerfile for EMSDK
+
+This Dockerfile builds a self-contained version of Emscripten SDK that enables Emscripten to be used without any
+other installation on the host system.
+
+It is published at https://hub.docker.com/r/emscripten/emsdk.
+
+### Usage
+
+Simple usage of this container to compile a hello-world
+```bash
+# create helloworld.cpp
+cat << EOF > helloworld.cpp
+#include <iostream>
+int main() {
+  std::cout << "Hello World!" << std::endl;
+  return 0;
+}
+EOF
+```
+
+```bash
+# compile with docker image
+docker run \
+  --rm \
+  -v "$(pwd):$(pwd)" \
+  -u $(id -u):$(id -g) \
+  emscripten/emsdk \
+  emcc helloworld.cpp -o helloworld.js
+
+# execute on host machine
+node helloworld.js
+```
+
+Teardown of compilation command:
+
+|part|description|
+|---|---|
+|`docker run`| A standard command to run a command in a container|
+|`--rm`|remove a container after execution (optimization)|
+|`-v "$(pwd):$(pwd)"`|Mounting current folder from the host system into mirrored path on the container<br>TIP: This helps to investigate possible problem as we preserve exactly the same paths like in host. In such case modern editors (like Sublime, Atom, VS Code) let us to CTRL+Click on a problematic file |
+|`-u $(id -u):$(id -g)`| Run the container as a non-root user with the same UID and GID as local user. Hence all files produced by this are accessible to non-root users|
+|`emscripten/emsdk`|Get the latest tag of this container|
+|`emcc helloworld.cpp -o helloworld.js`|Execute `emcc` command with following arguments inside container, effectively compile our source code|
+
+
+
+### Building Dockerfile
+
+This image has following optional arguments
+
+| arg | default value | description |
+| --- | --- | --- |
+| `EMSCRIPTEN_VERSION` | `tot`<br/>(special case, tip-of-tree) | One of released version of Emscripten. For example `2.0.0`<br/> Minimal supported version is **1.39.0** |
+
+**Building**
+
+This step will build Dockerfile as given tag on local machine
+```bash
+# using docker
+docker build \
+    --network host \
+    --build-arg=EMSCRIPTEN_VERSION=1.39.17 \
+    -t emscripten/emsdk:1.39.17 \
+    -f docker/Dockerfile \
+    .
+```
+```bash
+# using predefined make target
+make version=1.39.17 build test
+```
+
+**Tagging**
+
+In case of using `docker build` command directly, given `--tag` should match version of released Emscripten (you can see list of non-legacy versions by executing `emsdk list`).
+
+**Pushing**
+
+This step will take local image and push to default docker registry. You need to make sure that you logged in docker cli (`docker login`) and you have rights to push to that registry.
+
+```bash
+# using docker
+docker push emscripten/emsdk:1.39.17
+```
+```bash
+# using predefined make target
+make version=1.39.17 push
+```
+
+In case of pushing the most recent version, this version should be also tagged as `latest` and pushed.
+```bash
+# using docker cli
+docker tag emscripten/emsdk:1.39.17 emscripten/emsdk:latest
+docker push emscripten/emsdk:latest
+
+```bash
+# using make
+make version=1.39.17 alias=latest push
+```
+
+### Extending
+
+If your project uses packages that this image doesn't provide you might want to:
+* Contribute to this repo: Maybe your dependency is either non-intrusive or could be useful for other people
+* Create custom image that bases on this image
+
+1. create own Dockerfile that holds:
+    ```dockerfile
+    # Point at any base image that you find suitable to extend.
+    FROM emscripten/emsdk:1.39.17
+
+    # Install required tools that are useful for your project i.e. ninja-build
+    RUN apt update && apt install -y ninja-build
+    ```
+
+2. build it
+    ```bash
+    docker build -t extended_emscripten .
+    ```
+
+3. test
+    ```bash
+    docker run --rm extended_emscripten ninja --version
+    # 1.10.0
+    ```