URL whitelisting on DLT means registering every link, APK, OTT link or call-back number that appears in your SMS, so the operator's scrubbing check can match it. Senders upload the links and give an undertaking that they are not malicious. A template can be approved and still fail at delivery if the link inside it is not whitelisted.
By Rohit Jadhav. Last reviewed 25 October 2026. This is operational guidance, not legal advice. Portals differ in how they take links, so confirm the screens and limits on your operator's portal.
Links are where a lot of SMS campaigns quietly fail. The template was approved, the sender ID is fine, the list is clean, and yet messages do not arrive, because the link in the text was never registered. This guide explains URL whitelisting on DLT: what must be whitelisted, how to do it and how to check it before a send. It is part of our main guide to DLT registration in India. For help with the set-up, Nexcomm's bulk SMS service includes registration support. More guides sit under Compliance & Regulations.
What is URL whitelisting?
It is the registration of links and call-back numbers with the DLT system so that messages carrying them can be delivered. TRAI's regulation describes the scrubbing function as processing messages that contain URLs, APKs, OTT links or call-back numbers using whitelisted data uploaded by the sender, provided the sender has given an undertaking that the whitelisted items are not malicious. In plain words: you tell the system which links you will use and promise they are safe, and messages with other links are stopped.
What do you need to whitelist?
- Website links in your messages, including landing pages and payment links.
- APK links if you send an app download.
- OTT links, such as links to messaging or streaming services, if you include them.
- Call-back numbers written in the message text.
How do you whitelist a link?
- Finish the basics first. You need a Principal Entity ID, an approved header and, ideally, your templates. See the main guide and SMS sender ID.
- Log in to the DLT portal and open the section for URL or link whitelisting.
- Enter each URL, APK link or number exactly as it will appear in your messages.
- Give the undertaking that the links are not malicious.
- Wait for approval, then load your link details into your SMS provider's dashboard along with your PE ID and template IDs.
The steps and screen names differ by portal. Ask your provider which portal you use and how it handles short links.
What about short links and tracking links?
Treat every distinct link as a separate item. If your tool creates a new short link for each recipient, registering each one is not practical, so ask your provider how it handles tracked links in DLT-compliant messages, and register the domain or pattern the portal accepts. Do not guess: an unregistered link is the commonest reason a promotional message with a link disappears. Using one stable, registered link is the simplest fix.
How do you check that links will go through?
- Compare the link in your template with the link you plan to send, character by character.
- Send a small test to your own numbers on the real route before the full campaign.
- Check delivery reports for the test and ask your provider for the failure reason if one does not arrive.
- Re-check whenever you change a landing page or domain.
A blocked message with a link often shows up as a failure at the scrubbing stage. See DLT scrubbing for what that stage checks, and DLT template rejected if the template itself was returned.
A worked example (hypothetical)
A furniture store in Jaipur sends a festival offer with a link to its sale page. This is an invented example. The template is approved, but the first test message to the owner's phone does not arrive. The provider's report points to the link. The store whitelists the sale page URL, gives the undertaking and loads the link details into the dashboard. The next test arrives, and the full campaign goes out. For the second campaign it keeps the same registered link instead of creating a new one.
Common mistakes with links
- Assuming an approved template means the link is approved. They are separate.
- Changing the link after registration. The new one needs whitelisting.
- Using a different short link for each campaign. Each may need registering.
- Whitelisting a link you do not control. The undertaking is your promise.
- Forgetting call-back numbers. They are covered too.
- Not testing. Send a small batch first.
Frequently asked questions
Why is my SMS with a link not delivered?
Often because the link is not whitelisted on DLT. Messages containing URLs, APKs, OTT links or call-back numbers are checked against whitelisted data uploaded by the sender. Register the link, load it into your provider and test again.
What is the undertaking for whitelisted links?
A declaration by the sender that the whitelisted URLs, APKs and OTT links are not malicious. The regulation makes it a condition of using the whitelisted data in scrubbing.
Do I need to whitelist a phone number in my SMS?
Call-back numbers in message text are covered by the same scrubbing check. Confirm with your portal how to register them.
Can I use any short link service?
Only if the short link or its domain is registered and your provider supports it. Ask before you use a tracking or shortening tool in a DLT campaign.
How long does link whitelisting take?
It varies by portal, and we do not have a reliable figure to give you. Whitelist links before your campaign date, and test with a small batch.
Sources checked
All checked on 25 October 2026.
- TRAI, consolidated Telecom Commercial Communications Customer Preference Regulations, 2018 (scrubbing of messages containing URLs, APKs, OTT links and call-back numbers using whitelisted data; sender undertaking)
- Operator DLT portals: the whitelisting step as supplied by Nexcomm's team; confirm on the portal
If you are setting up links for a campaign and want to talk it through, you can reach our team through the contact page.