Docker built-in way to download a file

The Old Way: Installing curl

FROM alpine:latest
WORKDIR /app
RUN apk add --no-cache curl
RUN curl -sS https://example.com/somefile.txt -o /app/somefile.txt

EXPOSE 8080

The Better Way: Using Docker’s ADD Instruction

FROM alpine:latest
WORKDIR /app
ADD https://example.com/anotherfile.json /app/anotherfile.json

EXPOSE 8080

When to Use Each Approach ¹
- Use ADD when:
  - You’re downloading a single file from a URL
  - The file doesn’t require authentication
  - You want to keep your image minimal
- Stick with curl or wget when:
  - You need more control over the download (headers, authentication, retries)
  - You’re fetching multiple files in a complex workflow
  - You need to process or validate the downloaded content before using it