# CNAME chain checker: loops, apex aliases and flattening

> Follow a domain's CNAME chain, spot repeated names and apex aliases, and check for possible flattening. Free, bounded DNS checks with no signup.

- Canonical HTML page: https://dodomain.io/tools/cname-chain
- This Markdown twin: https://dodomain.io/tools/cname-chain.md
- Site index for agents: https://dodomain.io/llms.txt
- Full documentation as Markdown: https://dodomain.io/docs/llms-full.txt

Generated at build time from the same React source the HTML page renders, never a hand-maintained second copy. Every public page on this host has a twin at `<url>.md`.

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Free tools

## CNAME chain checker

Follow a hostname's aliases and see loops, apex CNAMEs and signs of flattening.

### How it works

1. **Enter the hostname.** Use the full name, such as www.example.com, without a URL scheme or path.
2. **Follow the aliases.** The engine reads each CNAME target until the chain ends, a name repeats, a lookup fails, or the limit of ten CNAME queries is reached.
3. **Read the flags.** Review apex aliases, loops, addresses and possible flattening before editing the record at your DNS provider.

### Use the free API

No API key required. Omit the Accept header for JSON. These read-only checks share a per-address rate limit; a 429 response means wait before trying again.

```
curl --get 'https://app.dodomain.io/api/tools/cname-chain' --data-urlencode 'name=www.example.com' -H 'Accept: text/markdown'
```

### Connecting a customer domain

DoDomain verifies DNS records inside your product's connect flow. Read the [apex-domain guide](https://dodomain.io/docs/apex-domains) before asking a customer to point a bare domain at a CNAME target.

### Frequently asked questions

#### What is a CNAME loop?

A loop occurs when following aliases returns to a name already visited. That circular chain never reaches a final target. A depth limit means the check stopped after its maximum number of hops; it does not prove a loop.

#### Can a CNAME sit at the zone apex?

A standard CNAME cannot coexist with the SOA and NS records required at a zone apex. Some providers offer ALIAS, ANAME or CNAME flattening instead, returning address records to DNS clients.

#### Can this prove a CNAME is flattened?

No. Addresses without a visible CNAME can indicate flattening or ordinary A/AAAA records. The tool labels flattening as suspected and cannot reveal a hidden target behind a proxy.

#### Does the checker change my DNS?

No. It only reads public DNS and applies bounded checks. You do not need an account, and a failed lookup is reported as incomplete rather than treated as proof that the record is missing.

### Start on the free plan

No card, no sales call: create an app, mint a session, and watch the first domain verify.

[Start with 50 free](https://app.dodomain.io/signin?mode=signup) [Read the quickstart](https://dodomain.io/docs)

### More free tools

- [DNS provider detector](https://dodomain.io/tools/provider-detector)
  
  Which DNS host serves a domain, and whether one-click setup is available there.
- [DNS propagation checker](https://dodomain.io/tools/dns-lookup)
  
  One record, read from the authoritative nameservers and three public resolvers.
- [SPF record checker](https://dodomain.io/tools/spf-checker)
  
  Parse a domain's SPF, walk its includes, count the lookups against the limit of ten.
- [Domain verification diagnoser](https://dodomain.io/tools/verify-diagnoser)
  
  Compare a domain with its expected target and find the provider's fix instructions.
- [DNS record diff](https://dodomain.io/tools/dns-diff)
  
  Compare a live DNS snapshot with the expected records you paste in.