> ## Documentation Index
> Fetch the complete documentation index at: https://tally.wharflab.com/llms.txt
> Use this file to discover all available pages before exploring further.

# hadolint/DL3020

> Use `COPY` instead of `ADD` for files and folders.

Use `COPY` instead of `ADD` for files and folders.

| Property | Value         |
| -------- | ------------- |
| Severity | Error         |
| Category | Best Practice |
| Default  | Enabled       |
| Auto-fix | Yes (`--fix`) |

## Description

For files and directories that do not require `ADD`'s tar auto-extraction capability, you should always use `COPY`. `COPY` is more transparent and
predictable than `ADD`, since it only supports basic copying of files into the container.

**Exception:** `ADD` is appropriate for local tar file auto-extraction into the image.

## Examples

### Problematic code

```dockerfile theme={null}
FROM python:3.4
ADD requirements.txt /usr/src/app/
```

### Correct code

```dockerfile theme={null}
FROM python:3.4
COPY requirements.txt /usr/src/app/
```

## Auto-fix

Replaces the `ADD` keyword with `COPY`, preserving all flags, sources, and destination unchanged.

* **Safe fix** (`FixSafe`): Always correct for local file/directory sources since `COPY` and `ADD` behave identically for non-URL, non-tar sources.

```dockerfile theme={null}
# Before
ADD --chown=app:app src/ /app/

# After (with --fix)
COPY --chown=app:app src/ /app/
```

The fix preserves instruction casing (`ADD` → `COPY`, `add` → `copy`).

## Reference

* [hadolint/DL3020](https://github.com/hadolint/hadolint/wiki/DL3020)