Number masking is a way of connecting two people by phone call or text message through an intermediary number, so that neither person sees the other’s real phone number. A ride-hailing passenger and a driver, a delivery customer and a courier, or a marketplace buyer and seller each see a number the platform controls. The platform relays calls and messages between them for as long as the session lasts. Number masking is usually built with a communications platform’s voice and messaging APIs or bought as a ready-made feature.
At a glance
- Each party calls or texts a number the platform controls, not the other person’s real number.
- The platform looks up who is in the session and forwards the call or message to the right person.
- Numbers usually come from a reusable pool and are tied to a session with a set lifetime.
- Calls and texts can be logged and, where permitted, recorded, which helps with disputes and quality.
- Privacy, recording and data-retention rules vary by jurisdiction and still apply.
What problem it solves
Many services depend on two people who don’t know each other talking briefly: a customer and a driver, a patient and a care worker, a homeowner and a contractor. Giving each of them the other’s personal phone number creates risks. Numbers can be misused for harassment, unwanted marketing or fraud after the job is over. In marketplaces, swapping numbers lets buyers and sellers move the deal off the platform. And if staff use personal mobiles to reach customers, the business has no record of what was said.
Number masking keeps the conversation inside a channel the business controls. Neither party learns the other’s number, the business can end access once the job is done, and calls and texts can be logged for support, dispute resolution or quality review.
How it works
Sessions. When two people need to talk, the platform creates a session that links their real numbers. Each person is assigned an intermediary number, sometimes called a proxy number, to use for that session.
Relaying calls. When one person calls the proxy number, the provider’s programmable voice service receives the call and asks your application what to do, often through a webhook. The application finds the session, and the provider places a second call to the other person and bridges the two. The person answering sees the proxy number as the caller, not the real number.
Relaying texts. Text messages work the same way through the provider’s messaging service: an SMS sent to the proxy number is forwarded to the other party from the proxy number. Business texting rules and registration requirements for those numbers still apply, and they vary by country.
Number pools. A proxy number only needs to be unique for a given person at a given time, so platforms reuse numbers across sessions. These are usually ordinary local or toll-free numbers, similar to direct inward dialing (DID) numbers on a phone system. Pool size depends on how many simultaneous sessions each person may have and how long sessions last.
Session end. When the job is done, the session expires. Later calls to the number can hear a message, reach a support line or be dropped, depending on how it is configured.
Caller identity. Because calls appear to come from the proxy number, name display services such as CNAM show whatever is registered for that number, if anything. Carriers may also label calls based on call authentication such as STIR/SHAKEN and on their own analytics, so masked calls can occasionally be marked as suspicious; how this works varies by carrier and country.
For buying guidance, see our communications platform as a service solution page.
When it matters for buyers
- Two-sided platforms. Ride-hailing, delivery, home services and marketplaces commonly use number masking to protect users and keep transactions on the platform.
- Field service and healthcare. Workers can reach customers or patients without exposing personal mobile numbers, with a business record of the contact.
- Building on a CPaaS. Some providers offer number masking as a ready-made service; on others, you build session logic yourself from voice and messaging APIs.
- Privacy reviews. Masking reduces what each party sees but creates call and message records the business must store and protect. Retention, recording consent and data protection rules vary by jurisdiction; involve counsel and your privacy team.
- Answer rates. If calls from proxy numbers go unanswered or are labelled as spam, number reputation and registration need attention.
Questions to ask vendors
- Do you offer number masking as a ready-made service, or do we build it from your voice and messaging APIs?
- How are proxy numbers assigned and reused, and how large a pool will we need for our volumes?
- Which countries and number types support masked calls and texts?
- How do we end a session, and what happens when someone calls an expired number?
- Can calls be recorded and texts logged, and how do we control consent prompts and retention?
- How do you help keep proxy numbers from being labelled as spam?
- What call and message records do you keep, where, and for how long?
How it differs from programmable voice
Programmable voice is the general set of APIs for placing, receiving and controlling phone calls from software. Number masking is one application built on those APIs, together with messaging, to relay calls and texts between two people through an intermediary number. Some CPaaS providers package number masking as its own product with session management included; with others, number masking is a pattern your developers assemble from voice and messaging building blocks.