While Fedify is primarily known as a framework for building ActivityPub servers, it also comes with a powerful command-line tool called fedify for debugging and testing ActivityPub implementations. Whether you're using the Fedify framework or not, this CLI tool can be invaluable for ActivityPub development.

Installation

Before diving into the features, you'll need to install the fedify command. You have several options:

Using npm (Node.js):

npm install -g @fedify/cli

Using Bun:

bun install -g @fedify/cli

Using Deno:

deno install -A --unstable-fs --unstable-kv --unstable-temporal -n fedify jsr:@fedify/cli

You can also download pre-built executables from the releases page.

For more detailed installation instructions and requirements, see the official documentation.

Smart Object Lookup

The fedify lookup command is smarter than it looks—it can handle various formats of the same identifier and provides multiple output formats to suit your needs:

# Three equivalent ways to look up the same actor:
fedify lookup @[email protected]
fedify lookup [email protected]
fedify lookup acct:[email protected]

# View the raw JSON response:
fedify lookup --raw @[email protected]

# Get a compact JSON-LD representation:
fedify lookup --compact @[email protected]

# See the fully expanded JSON-LD:
fedify lookup --expanded @[email protected]

Some ActivityPub servers require authorized fetch (also known as “secure mode”), which means all HTTP GET requests must be signed—even for public content. The -a/--authorized-fetch flag helps with this:

fedify lookup --authorized-fetch @[email protected]

This spins up a temporary ActivityPub server and signs the request with its key. This is particularly useful when:

• Accessing servers that require signatures for all requests (like certain Mastodon instances in secure mode)
• Fetching non-public content like followers-only posts (assuming you have permission)
• Testing how your server behaves with signed requests

Interactive Inbox Testing

The fedify inbox command not only provides a quick way to test federation but also comes with a powerful web interface for inspecting incoming ActivityPub activities. When you receive an activity, it shows you everything about the request, including:

• HTTP method and headers
• Request body (in multiple formats)
• Response details
• Server logs

You can see the raw HTTP headers that other servers send, which is invaluable when debugging signature verification issues or content negotiation problems. The interface includes tabs for viewing the activity in different formats:

• Raw HTTP request/response
• Compact Activity (normalized JSON-LD)
• Expanded Activity (fully expanded JSON-LD)
• Raw Activity (as received)
• Server logs

The command is highly configurable—you can control which follow requests to accept:

# Only accept follows from specific actors
fedify inbox -a @[email protected] -a @[email protected]

# Accept all follow requests
fedify inbox -a "*"

Rich NodeInfo Visualization

The fedify node command helps you understand how other instances are configured by visualizing their NodeInfo data in a user-friendly format:

# Show standard NodeInfo data with server icon
fedify node mastodon.social

# Include extra metadata that instances expose
fedify node -m mastodon.social

# Try to parse non-compliant NodeInfo responses
fedify node --best-effort problematic-instance.social

# Skip favicon fetching for faster results
fedify node --no-favicon mastodon.social

Flexible Local Development

For testing your ActivityPub implementation locally, the fedify tunnel command lets you temporarily expose your local server to the internet. You can choose from multiple tunneling services if the default one isn't working well:

# Use the default service
fedify tunnel 3000

# Use an alternative service
fedify tunnel --service serveo.net 3000

Shell Integration

Save yourself some typing by enabling shell completions—available for bash, fish, and zsh:

# For bash
source <(fedify completions bash)

# For fish
source (fedify completions fish | psub)

# For zsh
source <(fedify completions zsh)

Coming in Fedify 1.3.0: Custom User-Agent Support

The upcoming Fedify 1.3.0 release will include a feature to set custom User-Agent headers, which is helpful for tracking your requests in server logs:

# Set a custom User-Agent for lookup
fedify lookup --user-agent "MyApp/1.0" @[email protected]

# Set a custom User-Agent for NodeInfo requests
fedify node --user-agent "MyApp/1.0" mastodon.social

These features might not be immediately obvious when you first start using the Fedify CLI, but they can be incredibly helpful when debugging federation issues or testing your ActivityPub implementation.