How Platforms Detect VoIP and Disposable Numbers (and Flag Your Logins)
Platforms reject VoIP and disposable numbers because they are seen as high-risk for fraud, spam, and account abuse. These numbers are easy to obtain, often shared, and lack the verified identity tied to traditional mobile numbers. Detection methods include carrier lookups, number range analysis, and activity monitoring. To avoid verification failures, use a real-SIM mobile number from a major carrier like Verizon or AT&T, as these are trusted by platforms for their reliability and security.
- Why VoIP Numbers Fail: Platforms flag them as high-risk due to ease of access, lack of identity verification, and potential for abuse.
- Detection Methods: Carrier databases, prefix checks, porting history, and activity patterns help platforms identify VoIP and disposable numbers.
- Solution: Use a real-SIM mobile number for reliable verification and avoid disposable or shared numbers.
For hassle-free verification, ensure your number is tied to a major carrier and not classified as VoIP or disposable.
How Websites Classify Phone Numbers
When you sign up for a platform, your phone number is quickly categorized as VoIP, mobile, or landline. This classification plays a key role in assessing risk and preventing fraud. Generally, mobile numbers from major carriers like Verizon, AT&T, or T-Mobile are considered more trustworthy. On the other hand, VoIP numbers from services such as Google Voice or RingCentral are often flagged as higher risk and may even be rejected.
Let’s break down the types of phone numbers and the data sources that power their classification.
VoIP, Mobile, and Landline Numbers
Mobile numbers are tied to physical SIM cards issued by major carriers. When you get a mobile number, the carrier verifies your identity and links the number to your account, device, and billing information. Because of this accountability, mobile numbers are harder to acquire in bulk without proper checks, making them a reliable option for verification.
Landline numbers are connected to fixed-line networks and specific locations. While they are legitimate, they’re rarely used for SMS verification since traditional landlines don’t typically support texting. Even when they do, workarounds by carriers can make them less secure for verification purposes.
VoIP numbers operate over the internet and don’t rely on physical SIM cards or traditional carrier systems. Providers like Google Voice, TextNow, and RingCentral offer these numbers, which are easy to obtain and manage through apps or websites. However, this convenience also makes them more susceptible to misuse. Although VoIP numbers are great for everyday calling, their accessibility often leads platforms to reject them for verification.
Platforms distinguish these number types because each carries a different level of risk. Mobile numbers generally indicate a verified connection to a device and carrier, while VoIP numbers are seen as more prone to abuse.
Now, let’s look at the databases that help classify these numbers.
Data Sources Behind Number Classification
When you submit your phone number for verification, platforms tap into specialized databases that store detailed information about numbers within the North American Numbering Plan (NANP). These databases provide insights that help classify your number in real time.
- Carrier lookup databases: These databases offer information about the line type (mobile, VoIP, landline, or toll-free), carrier name, activation status, and porting history. For instance, when you enter your number into a banking app, a query instantly retrieves metadata about your number, including its type and associated carrier, before sending a verification code.
- Local Number Portability (LNP) databases: LNP data tracks when a number is ported from one carrier to another. For example, if a number originally issued by AT&T is moved to Google Voice, this change is recorded and reflected in carrier lookup services.
- Carrier identification databases: Managed by the North American Numbering Plan Administration (NANPA), these databases assign number ranges to specific carriers. This allows platforms to identify the likely carrier based on number prefixes, aiding in classification.
- Real-time queries: Using protocols like SS7, platforms can confirm whether a number is active, registered on a network, and capable of receiving SMS. This step is particularly important for high-stakes verifications.
These databases are constantly updated as numbers change carriers or are reassigned. For example, a mobile number could later be reclassified as VoIP if it’s ported to a VoIP provider. This dynamic nature highlights the need for up-to-date information to ensure accurate classification.
To make this process accessible, third-party services aggregate these data sources and offer APIs, allowing even smaller platforms to implement robust classification and fraud prevention systems. For U.S. numbers, the accuracy of these databases is typically high due to consistent updates and carrier reporting. This explains why VoIP numbers, despite their usefulness for regular calls, are often flagged and blocked during SMS verification.
How Platforms Detect VoIP Numbers
When you input your phone number on a platform, it undergoes a series of checks to determine if it’s a VoIP or mobile number. While the exact methods are kept under wraps, platforms generally rely on carrier data, number ranges, and historical records to make the distinction.
Carrier and Line-Type Lookups
A key strategy involves analyzing carrier records to identify the type of line associated with a number. This data reveals whether a number belongs to a mobile network or a VoIP provider. Numbers showing VoIP characteristics are often flagged and rejected - sometimes before a verification code is even sent.
Platforms also pay close attention to specific patterns in numbers, further helping them identify virtual lines.
Number Range and Prefix Patterns
Platforms often maintain internal databases of number ranges commonly linked to VoIP services. Numbers falling into these ranges are flagged during the verification process. This method enables platforms to quickly spot numbers that are less likely to comply with SMS verification standards.
Porting and History Checks
Another factor platforms examine is a number’s history, including recent carrier changes or porting activity. For instance, if a number originally belonged to a mobile carrier but was later switched to a VoIP provider, it raises a red flag. By reviewing historical data, platforms add an extra layer of scrutiny to reduce the chances of VoIP numbers passing verification.
These combined checks work together to efficiently detect and block numbers that don’t meet verification standards. This explains why VoIP services like Google Voice or TextNow often fail SMS verification. To avoid this, using a real-SIM number - recognized as a mobile line - ensures it bypasses the filters that flag virtual numbers.
Want to learn more about real-SIM numbers? Check out our Real-SIM numbers page for additional insights.
Detecting Disposable and Shared SMS Numbers
Platforms have developed methods to identify disposable and shared SMS numbers, as these types of numbers present a higher risk. Why? They’re often used by multiple people or made publicly available, which significantly increases the chances of fraud.
Known Disposable and Shared Pools
To combat this, platforms maintain extensive databases of disposable and shared SMS numbers. These lists are frequently updated across the industry to prevent fraudulent account creation. When you enter a phone number, the platform cross-references it with these databases. If the number has been linked to multiple users in the past, it’s often flagged before a verification code is even sent.
But detection doesn’t stop there. Platforms also monitor numbers that appear on public SMS-receiving websites - those sites where anyone can view incoming messages without logging in. Numbers found on such sites are typically blocked from verification immediately. This is especially crucial for financial institutions and secure apps, which view these numbers as a serious security risk.
Another red flag? Numbers that are recycled rapidly. If a number changes hands multiple times in a short period, it’s more likely to be part of a temporary or shared pool rather than belonging to a single individual.
These checks are bolstered by behavioral analyses, which work alongside static detection methods to identify suspicious activity.
Velocity and Abuse Patterns
Platforms also monitor how often a phone number is used for account verifications. Genuine mobile numbers tend to have low verification activity over time. In contrast, disposable numbers are often linked to many accounts in quick succession, which raises abuse flags. Platforms evaluate factors like account type, registration timing, and subsequent behavior. If a number is rapidly tied to multiple accounts - especially if those accounts display shady behavior - it’s flagged as high risk.
Repeated verification failures further reinforce a number’s risk profile.
Geographic inconsistencies can also reveal shared usage. For example, if a number is used to create accounts in widely separated locations, it’s a strong indicator of shared or disposable status. Similarly, time zone and device mismatches are scrutinized. A U.S.-based number, for instance, might raise suspicion if it’s mostly active during hours that don’t align with local time or is linked to various devices.
This explains why services like Google Voice often fail verification on platforms with strict security requirements, such as messaging apps, banking systems, and cryptocurrency exchanges.
All of these factors underscore why choosing a reliable, individually assigned mobile number is so important. Numbers built on carrier networks, like Real-SIM numbers, are far more likely to be accepted for verification because they avoid the pitfalls of virtual or shared lines.
sbb-itb-070b8f8
Why VoIP Services Fail Verification
If you’ve ever tried using services like Google Voice or RingCentral to verify an account on platforms like WhatsApp, Coinbase, or your bank’s app, you’ve probably come across an error like: "This number cannot be used for verification." It’s a frustrating experience, especially since these numbers handle regular calls and texts just fine. So, why do these platforms reject VoIP numbers for verification?
It all comes down to how these numbers are classified and the security concerns associated with them.
How Platforms Classify VoIP Numbers
When platforms perform a carrier lookup, they identify the type of phone number being used. VoIP numbers are flagged differently from traditional mobile numbers, and here’s why:
VoIP numbers are seen as higher risk. They’re easy to obtain, don’t require a physical SIM card, and aren’t tied to a specific mobile carrier. On top of that, they can be quickly recycled or reassigned. Signing up for a VoIP service takes minutes, often with little to no identity verification. This makes them a favorite tool for fraudsters looking to create multiple accounts quickly. Unlike traditional mobile numbers, VoIP numbers lack the long-term identity connection that helps tie them to a real person. For example, if someone stops paying for a Google Voice number, it can be reassigned to another user, which can lead to major verification headaches - imagine receiving someone else’s verification code while trying to access your account.
Because of these risks, platforms like WhatsApp, Stripe, and banking apps often block VoIP numbers outright or enforce stricter verification protocols. In many cases, they won’t even attempt to send a verification code once they detect the number’s classification.
Common Issues with VoIP Verification
The most common problem users face is immediate rejection. Messages like "This number cannot be used for verification" or "Invalid phone number" pop up because the platform’s carrier lookup flags the number as VoIP and blocks it before sending any one-time password (OTP).
Even when a VoIP number isn’t outright rejected, verification codes may be delayed or fail to arrive altogether. This delay happens because VoIP numbers rely on internet-based routing, which can be inconsistent. For time-sensitive tasks - like completing a financial transaction or recovering a locked account - this delay can be more than just inconvenient; it can be costly.
Platforms vary in how they handle VoIP numbers, depending on their risk tolerance. Services like OpenPhone, Sideline, and Burner often encounter the same issues. While these tools are excellent for managing business calls or juggling multiple lines, their VoIP foundation is what gets them flagged during verification.
Real-SIM Numbers vs. VoIP Numbers
To avoid these problems, real-SIM numbers provide a clear advantage over VoIP numbers. The key difference lies in how they connect to carrier networks.
Real-SIM numbers are tied to a physical SIM card and connect directly to a mobile carrier’s network. This creates a reliable and verifiable link between the number, the carrier, and the user. When platforms perform a carrier lookup on a real-SIM number, they recognize it as a traditional mobile line, which is trusted for verification purposes.
In contrast, VoIP numbers operate purely through software and depend on internet routing rather than cellular infrastructure. While this makes them cost-effective and flexible for business communication, it also makes them less reliable for verification systems.
Here’s why real-SIM numbers work better:
- Carrier Verification: Platforms can confirm that the number belongs to a major carrier like Verizon, AT&T, or T-Mobile, adding a layer of trust.
- Consistent Identity: Real-SIM numbers aren’t easily recycled or reassigned, reducing the risk of someone else receiving your verification codes.
- Lower Fraud Risk: Real-SIM numbers are harder to obtain and maintain, making them less appealing to fraudsters.
- Reliable Delivery: SMS messages sent to real-SIM numbers go through the carrier’s native messaging infrastructure, ensuring faster and more dependable delivery compared to the internet-based routing used by VoIP services.
For businesses or individuals who rely on secure and timely SMS verification - whether for account creation, two-factor authentication, or platform access - real-SIM numbers are the way to go. They eliminate the headaches caused by VoIP verification failures and meet the security requirements of today’s platforms.
Before attempting verification on platforms with strict requirements, it’s worth checking your number’s classification to save time and avoid delays. You can verify your number type here to ensure it meets the platform’s standards.
How to Choose a Phone Number That Passes Verification
When it comes to picking a phone number for SMS verification, making the right choice can save you from failed logins and unnecessary delays. Here's how to ensure your number meets platform requirements.
Check If Your Number Is VoIP or Mobile
Before attempting to verify an account, it’s important to know how your number is classified. Platforms rely on carrier lookups to determine whether a number is mobile, landline, or VoIP - and this classification plays a key role in whether it will be accepted.
You can use a lookup tool to check your number’s type, carrier, and line status. These tools identify VoIP numbers, while numbers from major carriers like Verizon, AT&T, or T-Mobile will typically show as mobile. For a quick check, you can verify your number type here; it only takes a minute and can save you a lot of hassle later.
If your lookup result says "Mobile" or "Wireless," your number is likely to pass most verification checks. On the other hand, if it shows terms like "VoIP," "Virtual," or "Fixed VoIP," platforms such as WhatsApp, Coinbase, and banking apps may reject it. Some tools also reveal the carrier name - seeing a major carrier like Verizon or T-Mobile is a good sign, whereas names like "Bandwidth" or "Twilio" typically indicate a VoIP number.
Here’s a simple way to differentiate: if your number operates purely over the internet and doesn’t require a physical SIM card, it’s classified as virtual or VoIP. In contrast, traditional mobile numbers are tied to a physical SIM card, which is what most platforms prefer for verification.
Once you’ve confirmed your number type, the next step is to ensure it’s solely dedicated to you.
Avoid Disposable and Shared Numbers
Numbers that are disposable or shared with others can create serious security risks. Disposable numbers are reassigned quickly, which means someone else could end up receiving your verification codes or password reset links. Shared numbers, used by multiple people at the same time, pose similar risks, especially for accounts that handle sensitive information.
For consistent and secure verification, it’s best to use a number that’s exclusively yours.
Benefits of Real-SIM Numbers
Real-SIM numbers, which are tied to physical SIM cards, offer a reliable and secure option for SMS verification. When a platform performs a carrier lookup on a real-SIM number, it sees a direct connection to a major carrier like Verizon, AT&T, or T-Mobile, which helps establish trust immediately.
These numbers are dedicated to a single user, ensuring stability for long-term account access. This is particularly important for platforms that require ongoing access, such as banking apps, cryptocurrency exchanges, and business tools.
Another advantage is the speed and reliability of SMS delivery. Messages sent to real-SIM numbers travel through the carrier’s native messaging infrastructure, which is faster and more dependable than the internet-based routing used by VoIP services. For time-sensitive tasks - like verifying a financial transaction, recovering a locked account, or setting up two-factor authentication - this reliability is crucial.
Real-SIM numbers are widely accepted, working with over 1,000 platforms, including Google, WhatsApp, Coinbase, Stripe, AWS, LinkedIn, and major banking apps.
If you’re tired of dealing with verification failures, switching to a real-SIM number can provide an immediate solution. Services like JoltSMS offer real-SIM, non-VoIP numbers specifically designed for SMS verification. These numbers are dedicated to you, never shared or recycled during your rental period, and come with a 99.9% delivery rate. Plus, they include unlimited inbound SMS and instant webhook delivery to platforms like Slack or Discord for seamless team access.
For those who rely on VoIP for business communications, you don’t have to give it up entirely. Keep your VoIP line for calls and use a real-SIM number strictly for verification. This way, you get the best of both worlds - without the headaches.
Conclusion
The strategies outlined above highlight why many platforms enforce strict phone number verification protocols.
VoIP and disposable numbers are often rejected because they open the door to spam, fraud, and bulk account creation. These types of numbers allow malicious users to set up multiple accounts, sidestep security measures, and operate with little accountability.
Platforms use several detection methods - like carrier lookups, number range analysis, and behavioral checks - to identify and block high-risk numbers. The outcome? Failed verifications, locked accounts, and wasted time for users relying on these numbers.
Real-SIM numbers, on the other hand, bypass these issues by directly connecting to major carriers like Verizon, AT&T, or T-Mobile. When a platform performs a carrier lookup on a real-SIM number, it detects a legitimate mobile connection, free from VoIP flags, shared pools, or suspicious activity. These numbers are categorized as mobile, dedicated, and reliable - precisely what platforms look for during SMS verification.
For high-security applications, such as banking or crypto platforms, using a real-SIM number is essential. It ensures error-free verification and dependable SMS delivery. These numbers are accepted by over 1,000 platforms, reducing the frustration of repeated verification failures.
Switching from VoIP to a real-SIM number is an effective way to avoid errors like "This number cannot be used for verification" and to secure uninterrupted account access.
FAQs
Why do platforms reject VoIP numbers during verification?
Platforms often reject VoIP numbers because they recognize them as virtual or non-physical, which are often linked to fraud or temporary usage. Unlike real-SIM numbers that are tied to physical devices, VoIP numbers are easier to get and much harder to trace, making them less reliable for verification purposes.
Many verification systems use carrier lookups and databases that track known VoIP ranges to flag these numbers. On top of that, disposable SMS services and free VoIP providers like Google Voice or TextNow are frequently misused, leading platforms to block them entirely. If you're facing rejections, it's likely because the platform specifically requires a real-SIM number to complete the verification process.
Why should I use a real-SIM number instead of a VoIP number for SMS verification?
Using a real-SIM number gives you a much better chance of successfully receiving SMS verification codes compared to VoIP numbers. Many websites and apps have systems in place to detect VoIP or disposable numbers, often blocking them from receiving verification messages. This happens because VoIP numbers are frequently associated with known ranges or disposable SMS services that raise red flags for potential fraud.
Real-SIM numbers, however, are linked to physical SIM cards, making them more reliable and widely accepted. They work effortlessly with platforms like WhatsApp, banks, and payment services - areas where VoIP numbers tend to fall short. If you’ve run into issues with services like Google Voice or TextNow, switching to a real-SIM number can eliminate those headaches and ensure your verifications go through without a hitch.
How can I check if my phone number is a VoIP or mobile number before using it for verification?
To find out if your phone number is a VoIP or mobile number, you can use carrier lookup tools. These tools analyze the number to determine its type and the carrier it’s linked to. For instance, they can identify if the number is part of a VoIP range, commonly used by services like Google Voice or TextNow, or if it’s tied to a mobile network with a physical SIM card.
Some platforms also flag numbers based on usage patterns or if they come from known disposable SMS pools. If your number often fails verification attempts, it may be classified as VoIP or disposable. To avoid issues with verification, it’s best to use a real-SIM mobile number, as these are generally accepted across most platforms for SMS verification.