---
title: "ICP custom domains: registration stuck with null canister_id"
url: https://blog.b3pay.net/icp-custom-domains-registration-stuck-with-null-canister-id
desk: Internet Computer
published_at: 2026-10-27T15:34:09.462Z
machine_written: true
read_token: mvr1vbcg.DF_fIR_m5AC9042BUEvp_LsJmKVE3jPuxI5y6F9pstk
read_token_expires_at: 2026-10-28T18:59:49.936Z
---

# ICP custom domains: registration stuck with null canister_id

> A forum report says an ICP custom domain stayed in 'registering' with a null canister_id for hours. Before you register, call the validate endpoint and check its canister_id. If a registration stalls, you can only poll its status. The docs list no timeout and no cancel call.

Key points:
- On 2026-10-26 the status API returned registration_status 'registering' with canister_id null for icpcoins.eu. It still showed that state 3 or 4 hours later.
- By 06:39 UTC on 2026-10-27 the same user reported the domain was working. No root cause or fix has been published in the thread.
- The custom domains docs list no timeout and no cancel call for an in-progress registration. A new POST can fail with 'conflict' while another task is running.
- Run GET /custom-domains/v1/{domain}/validate first, and do not POST until it returns your canister ID with validation_status 'valid'.

On 2026-10-26 a developer reported that a custom domain registration on ICP's HTTP gateway service was stuck. For hours, the status API returned `"registration_status":"registering"` with `"canister_id":null` for icpcoins.eu, and it cleared on its own by the morning of 2026-10-27. If you point a domain at a canister, validate your DNS records and ownership file before you send the registration request, because the docs give no way to cancel a registration once it has started.

## What happened

The report is in a forum thread opened on 2022-10-06. In that thread a boundary node team researcher, rbirkner, wrote on 2022-10-07 that custom domains would use "a CNAME in your DNS entry" plus a canister mapping, with TLS terminated at the boundary nodes. The feature has shipped since then. A redesigned REST API under `/custom-domains/v1/{domain}` was announced on the forum in November 2025.

On 2026-10-26 user Henn91 posted the status response for his domain:

```json
{"status":"success","message":"Registration status of the domain","data":{"domain":"icpcoins.eu","canister_id":null,"registration_status":"registering"}}
```

The facts from the thread, in order:

1. **2026-10-26, first post:** the status stays `registering`. He asks if there is a timeout or if DFINITY has to cancel the registration by hand, and says he cannot stop or delete it. He suggests an automatic delete after 30 minutes.
2. **2026-10-26, about two hours later:** "Now 3 or 4 hours passed, still stuck". He concludes that there is no expiry timer. He also says Caffeine users had domains stuck "for days" and thinks it may be the same bug. That link is his guess.
3. **2026-10-27, 06:39:** "Its working now". He asks for a fix so the service no longer returns success when `canister_id` is null, and says removing and re-adding a domain is slow.

DFINITY had not replied in the thread by that last post. No root cause has been published.

One detail matters if you read this response. In the official docs, a status query that works returns `"status": "success"` with the message "Registration status of the domain". So the top-level `success` means the status query worked. It does not mean the domain is registered. The useful signal is the pair inside `data`: `canister_id` is `null` while the status is `registering`. In the docs, both the validate response and the accepted registration response include the canister ID, so a `null` value means the service has no canister mapped to the domain.

## Who is affected and why it matters

This affects anyone who serves a canister frontend on their own domain through the HTTP gateways, including apps built with Caffeine. The docs list four states: `registering`, `registered`, `expired` and `failed`. The docs say registration "takes a few minutes". They do not say how long `registering` can last or what happens when it stalls.

The docs also leave no clean way out. A `POST` while another task is running can return `conflict` ("another registration task is in progress. Retry after a few minutes"). The documented removal steps start with deleting your `_canister-id` TXT record and `_acme-challenge` CNAME, then calling `DELETE`. If a registration stalls, you can poll, retry later or ask on the forum. As the reporter found, you cannot stop it yourself through the documented API.

The Internet Identity cost is real. II derives user principals from the origin. If users sign in at `<canister-id>.icp.net` today and you move them to a custom domain, they get new principals unless you set up alternative origins ("Use one derivation origin" in the docs).

## What to do now

These commands come from the current ICP custom domains guide, which uses the `icp.net` host. Replace `CUSTOM_DOMAIN` with your domain.

**Before registering:**

1. Add the three DNS records:

| Type | Host | Value |
|---|---|---|
| `CNAME` | `CUSTOM_DOMAIN` | `CUSTOM_DOMAIN.icp1.io` |
| `TXT` | `_canister-id.CUSTOM_DOMAIN` | your canister ID |
| `CNAME` | `_acme-challenge.CUSTOM_DOMAIN` | `_acme-challenge.CUSTOM_DOMAIN.icp2.io` |

2. Serve `/.well-known/ic-domains` from the canister, with one domain per line. On the legacy asset canister, add `{ "match": ".well-known", "ignore": false }` to `.ic-assets.json5`.
3. Confirm the TXT record and the file from the outside:

```bash
dig TXT _canister-id.CUSTOM_DOMAIN
curl -sL https://<canister-id>.icp.net/.well-known/ic-domains
```

You need exactly one `_canister-id` TXT record. If you use Cloudflare for DNS, turn off Universal SSL and set the records to "DNS only".

4. Validate, and do not continue until the response shows your canister ID and `"validation_status": "valid"`:

```bash
curl -sL -X GET "https://icp.net/custom-domains/v1/CUSTOM_DOMAIN/validate" | jq
```

**Register and watch:**

```bash
# Register
curl -sL -X POST "https://icp.net/custom-domains/v1/CUSTOM_DOMAIN" | jq

# Poll status: registering -> registered
curl -sL -X GET "https://icp.net/custom-domains/v1/CUSTOM_DOMAIN" | jq
```

The `POST` response should repeat your canister ID. If a status response shows `canister_id: null`, check the TXT record again with `dig`. The docs give no timeout, so if the record stays `null` and `registering`, post the domain and the full status response on the forum.

**To change or remove a mapping later:**

- To point the domain at another canister, change the `_canister-id` TXT record, then send `curl -sL -X PATCH "https://icp.net/custom-domains/v1/CUSTOM_DOMAIN" | jq`.
- To remove the domain, delete the TXT and `_acme-challenge` records, then send `curl -sL -X DELETE "https://icp.net/custom-domains/v1/CUSTOM_DOMAIN" | jq`. After that, a status `GET` should return 404.

On the frontend, set the agent host when the app runs on a custom domain. Otherwise the agent sends API calls to the page origin, and those calls fail:

```js
import { HttpAgent } from "@icp-sdk/core/agent";
const isProduction = process.env.NODE_ENV === "production";
const host = isProduction ? "https://icp-api.io" : undefined;
const agent = await HttpAgent.create({ host });
```

## Caveats

This is one user's report. The thread does not say what caused the stall or whether anything was changed on the service side. The reporter thinks the earlier Caffeine domain delays were the same bug, but that has not been confirmed. Once `registered` appears, the docs say to allow 5 to 10 more minutes for the change to reach all HTTP gateways.

## Sources

1. [Boundary nodes - custom domains / canisters with IP addresses?](https://forum.dfinity.org/t/boundary-nodes-custom-domains-canisters-with-ip-addresses/15777)
2. [Custom domains | ICP Developer Docs](https://docs.internetcomputer.org/building-apps/frontends/custom-domains/using-custom-domains)
3. [Custom Domains Redesign: New API Available](https://forum.dfinity.org/t/custom-domains-redesign-new-api-available/59790)

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