How to Block Your Mobile Number When Making Calls

Most people assume their phone number is automatically visible to whoever they call. It usually is — but it doesn't have to be. Blocking your mobile number is a straightforward process, and it works across virtually every carrier and device type. The specifics, though, depend on a handful of variables that matter more than most guides let on.

What "Blocking Your Number" Actually Means

When you block your number, you're instructing the network to withhold your Caller ID information from the recipient's phone. Instead of seeing your number, the person you're calling sees "No Caller ID," "Private Number," "Unknown," or a similar label depending on their carrier and device.

This is done through a signaling mechanism called CLIR — Calling Line Identification Restriction. It's a standard feature built into the global telephone network (both cellular and landline), not a workaround or hack. You're not hiding anything suspicious; you're using a legitimate network-level privacy control.

It's worth knowing upfront: blocking your number doesn't guarantee anonymity. Emergency services (like 911 or 999) can still see your number regardless of CLIR settings. Some carriers and businesses use services that bypass Caller ID suppression entirely. And call logs on the receiving carrier's end may still record the call.

The Two Main Ways to Block Your Number 📵

1. Per-Call Blocking (Prefix Code)

The fastest method is adding a prefix code before the number you're dialing. This only blocks your number for that single call — your Caller ID returns to normal on the next one.

How it works: Dial the prefix, then the full number including country or area code. For example, in the US: *67 + 555-867-5309. The call goes through normally — you just appear as "Private" or "Unknown" on the other end.

This method works on virtually all smartphones and basic handsets regardless of operating system or carrier. It requires no settings changes and no account access.

2. Permanent Number Blocking (Settings or Carrier-Level)

If you want your number hidden by default on every outgoing call, you have two routes:

Through your phone's settings:

• iOS (iPhone): Go to Settings → Phone → Show My Caller ID → toggle off.
• Android: Open the Phone app → Settings (or three-dot menu) → Calls → Additional Settings → Caller ID → select "Hide number."

The exact path varies by Android manufacturer. Samsung, Pixel, and OnePlus devices all handle this slightly differently. Some Android skins bury this option deeper or label it differently — if you can't find it, searching "Caller ID" within your phone's Settings search bar usually surfaces it.

Through your carrier: Some carriers allow you to request permanent CLIR at the account level — meaning it applies even if your device settings don't support the toggle, or across multiple lines on a business account. This typically requires a call to customer support or a visit to your account portal. A few carriers charge a small monthly fee for this; most don't.

Variables That Change How This Works 🔧

Understanding the method is the easy part. Whether it works the way you expect depends on several factors:

Your carrier's implementation: Most major carriers support CLIR fully, but MVNOs (budget carriers that ride on larger networks) occasionally have inconsistent implementations. If you're on a smaller carrier, it's worth testing before relying on it.

VoIP and app-based calls: If you're calling through WhatsApp, FaceTime Audio, Google Voice, or another internet-based service, the *67 prefix and device Caller ID settings typically don't apply. Each platform handles caller identification its own way. Google Voice, for instance, shows the Google Voice number you've been assigned — not your underlying mobile number — regardless of your device settings.

The recipient's setup: Some businesses and individuals subscribe to services that unblock or reveal suppressed numbers. If someone has configured their line to reject calls from private numbers, your call may not connect at all, or they may receive a message explaining that private calls are blocked.

Dual-SIM devices: If your phone runs two SIMs, Caller ID settings typically apply per SIM. Blocking your number on SIM 1 doesn't automatically apply to calls made from SIM 2.

Your region's regulations: In some countries, CLIR is restricted in certain contexts — for example, it may be automatically overridden for calls to financial institutions or emergency lines. These are network-level rules you can't override from the device.

When Per-Call vs. Permanent Blocking Makes Sense

Per-call blocking suits people who occasionally want privacy — calling a seller on a marketplace app, responding to a classified ad, or reaching out to someone you don't yet know well. Your number stays visible to contacts and people you regularly call.

Permanent blocking is more practical if you routinely call strangers professionally — journalists, researchers, investigators, or anyone whose work involves a high volume of outbound calls to unknown recipients. It removes the friction of remembering a prefix every time.

The tradeoff with permanent blocking: some recipients will simply not answer calls from private numbers, and certain services (banks, healthcare portals, two-factor auth callbacks) may not function correctly if they can't verify your number.

One More Layer: Temporary Numbers and Call Apps

For situations where even CLIR feels insufficient — or when you need a number that can receive calls and texts, not just block outgoing Caller ID — some people use virtual number apps or second-number services. These give you a separate number entirely, which means the recipient sees a real (but different) number rather than "Unknown."

This is a meaningfully different approach from blocking your number, with its own tradeoffs around cost, setup, and the level of separation it actually provides.

The right method depends heavily on why you want to block your number, how often, and whether you need a one-way (outgoing-only) privacy measure or something more comprehensive. Those specifics sit entirely within your own situation.