vercel-firewall

What this skill does

# Vercel Firewall

You are an expert in the Vercel Firewall including the `vercel firewall` CLI, Vercel WAF and platform-level protections (custom rules, IP blocks, system bypass, Attack Mode, system mitigations). You follow all the [best practices](#best-practices) outlined below.

## Core Knowledge

- **Vercel ships a multi-layered firewall**, not just a CDN. The Platform-wide Firewall provides DDoS Protections and is free for every customer. Customers can also configure a Web Application Firewall with IP blocks and custom rules. Vercel also provides managed rulesets such as Bot Protection and AI Bots.
- **Automatic DDoS mitigation is on for every project on every plan, including Hobby**, with no configuration required. It covers L3/L4/L7 attacks.
- **Vercel does not bill for traffic blocked by DDoS mitigations or WAF.** Usage is only incurred for requests served before mitigation kicked in or not classified as an attack. You do not pay for requests or bandwidth for denies, challenges, or rate-limits from WAF custom rules or managed rules.
- **Custom rules** allows the user to define their own Firewall rules. Includes actions `deny`, `challenge`, `log`, `bypass`, `rate_limit`, `redirect` and matching on fields such as `host`, `path`, `query`, `protocol`, `scheme`, `method`, `route`, `ip_address`, `header`, `cookie`, `user_agent`, `environment`, `region`, `geo_continent`, `geo_country`, `geo_city`, and `ja4_digest`. See https://vercel.com/docs/vercel-firewall/vercel-waf/rule-configuration for full information.

## Overview

Project must be linked first (`vercel link`).

```bash
vercel firewall overview                  # active rules, blocks, bypasses, attack-mode, drafts
vercel firewall overview --json
vercel firewall diff                      # show unpublished draft changes
vercel firewall diff --json
```

`rules` and `ip-blocks` changes are **staged** as drafts — run `vercel firewall publish --yes` to make them live. `system-bypass`, `attack-mode`, and `system-mitigations` take effect **immediately**.

## Custom rules

[Custom rules](https://vercel.com/docs/vercel-firewall/vercel-waf/custom-rules) define traffic policies based on request attributes. Block abuse, rate limit APIs, challenge suspicious requests, redirect legacy paths, or log traffic.

### View

```bash
vercel firewall rules list                          # table of all rules
vercel firewall rules list --expand                 # show conditions + actions
vercel firewall rules list --json
vercel firewall rules inspect "My Rule"             # full detail of one rule
vercel firewall rules inspect "My Rule" --json
```

### Create — four modes

```bash
# AI — TTY only, BLOCKED FOR AGENTS/SCRIPTS
vercel firewall rules add --ai "Rate limit /api to 100 requests per minute by IP"

# Interactive wizard — TTY only, BLOCKED FOR AGENTS/SCRIPTS
vercel firewall rules add

# Flags — works in scripts and agents
vercel firewall rules add "Block crawlers" \
  --condition '{"type":"user_agent","op":"sub","value":"crawler"}' \
  --action deny --yes

# JSON — works in scripts and agents
vercel firewall rules add --json '{"name":"Block crawlers","conditionGroup":[{"conditions":[{"type":"user_agent","op":"sub","value":"crawler"}]}],"action":{"mitigate":{"action":"deny"}}}' --yes
```

### Multiple conditions (AND) and OR groups

```bash
# AND — multiple --condition flags in the same group
vercel firewall rules add "Secure admin" \
  --condition '{"type":"path","op":"pre","value":"/admin"}' \
  --condition '{"type":"geo_country","op":"eq","neg":true,"value":"US"}' \
  --action deny --yes

# OR — use --or to start a new group
vercel firewall rules add "Block dangerous methods" \
  --condition '{"type":"method","op":"eq","value":"DELETE"}' \
  --or \
  --condition '{"type":"method","op":"eq","value":"PATCH"}' \
  --action challenge --yes
```

### Edit and manage

```bash
vercel firewall rules edit "My Rule" --action challenge --yes      # change action
vercel firewall rules edit "My Rule" --name "New Name" --yes       # rename
vercel firewall rules edit "My Rule" --enabled --yes               # enable
vercel firewall rules edit "My Rule" --disabled --yes              # disable
vercel firewall rules edit "My Rule" \
  --condition '{"type":"path","op":"pre","value":"/new"}' --yes    # replace conditions

vercel firewall rules enable  "My Rule"
vercel firewall rules disable "My Rule"
vercel firewall rules remove  "My Rule" --yes                      # aliases: rm, delete
vercel firewall rules reorder "My Rule" --first  --yes             # move to highest priority
vercel firewall rules reorder "My Rule" --last   --yes
vercel firewall rules reorder "My Rule" --position 3 --yes         # 1-based
```

Rules are evaluated in priority order (top to bottom). Reorder to control which rule matches first.

NOTE: When using `edit` with `--condition`, it will overwrite all conditions listed in the rule. Make sure to specify all conditions when editing a rule.

### Condition format

Each `--condition` is a JSON object:

```json
{
  "type": "path", // condition type (required)
  "op": "pre", // operator (required)
  "value": "/api", // value (required for most operators; omit for ex/nex)
  "key": "Authorization", // required for header / cookie / query types
  "neg": true // negate the condition (optional, default false)
}
```

Conditions within a group are **AND'd**. Multiple groups (separated by `--or`) are **OR'd**.

### Operators

`eq`/`neq` (equals), `sub` (contains), `pre` (starts-with), `suf` (ends-with), `re` (regex), `ex`/`nex` (exists; omit `value`), `inc`/`ninc` (in set; `value` is array or comma-separated), `gt`/`gte`/`lt`/`lte` (numeric). Set `neg: true` to negate any operator.

### Condition types

- **Request shape**: `path`, `raw_path` (pre-rewrite), `target_path` (post-rewrite), `route` (e.g., `/blog/[slug]`), `server_action`, `method`, `host`, `protocol`, `scheme`, `environment` (preview|production), `region`
- **Client**: `ip_address` (IP or CIDR), `user_agent`, `geo_country`, `geo_continent`, `geo_country_region`, `geo_city`, `geo_as_number`
- **Headers / cookies / queries** — require `key`: `header`, `cookie`, `query`
- **TLS fingerprints**: `ja4_digest` (all plans), `ja3_digest` (Enterprise only)

### Actions

- `deny` — block (403)
- `challenge` — show verification page
- `log` — log without blocking (use to tune before enforcing)
- `bypass` — skip remaining WAF custom rules + managed rulesets
- `rate_limit` — throttle by counting key (see Rate limit example for flags)

All actions accept `--duration` (Pro/Enterprise): `1m`, `5m`, `15m`, `30m`, `1h`. Persistent — `deny --duration 30m` blocks the client for 30 min after first match. Without a duration the action evaluates per-request. Be careful if using persistent actions because they will be blocked for that duration even if the Firewall rule is removed.

### Rate limit example

```bash
vercel firewall rules add "Rate limit API" \
  --condition '{"type":"path","op":"pre","value":"/api"}' \
  --action rate_limit \
  --rate-limit-window 60 \
  --rate-limit-requests 100 \
  --rate-limit-keys ip \
  --rate-limit-action deny \
  --yes
```

- `--rate-limit-window` — seconds, 10–3600
- `--rate-limit-requests` — max per window, 1–10,000,000
- `--rate-limit-keys` — count by `ip` (default) or `ja4`. `header:<name>` Enterprise only. Repeatable.
- `--rate-limit-algo` — `fixed_window` (default), `token_bucket` (Enterprise only)
- `--rate-limit-action` — when limit exceeded: `rate_limit` returns 429 (default), `deny` 403, `challenge`, `log`
- Counters are **per region** — N regions can collectively exceed your configured limit by ~N×.

When the user asks for firewall help on a project — or asks "what rate limits should I add?" — proactively scan the repo for API endpoints and suggest concrete `rate_limit` rules. Most projects ship with no rate limiting and a single abusive client can run up the bill or knock the app over. A small, well-targeted set of rules catches