Do They Really Need Your Date of Birth? How to Share Less Personal Data Online

A practical way to protect personal information online is surprisingly simple: give organisations less information to lose in the first place.

We are used to filling in forms. Full name. Date of birth. Mobile number. Main email address. Home address. Employer. Sometimes we provide all of it without thinking much about why it is being requested.

Most of the time, the organisation asking is perfectly legitimate. The better question is not “Is this website a scam?” but something quieter:

Why does this service need this particular piece of information from me?

That does not mean inventing false identities everywhere or refusing to provide information whenever a form asks for it. Banks, insurers, airlines, public authorities and many regulated services genuinely need accurate information.

But a discussion forum may not need your legal name. A newsletter probably does not need your exact date of birth. An app may not need your mobile number simply because someone added a phone-number field to its registration form.

What does data minimisation mean?

Data minimisation is one of the core principles of the EU General Data Protection Regulation, or GDPR. The principle says that personal data collected by an organisation should be adequate, relevant and limited to what is necessary for the purpose for which it is being processed.

The European Commission explains that organisations should collect and process only the personal data necessary to fulfil a specific purpose. Spain's Agencia Española de Protección de Datos (AEPD) similarly describes privacy by default as minimising the amount of personal data, the extent of processing, the retention period and access to that data.

Legally, those obligations fall primarily on the organisation processing the data. But there is a useful consumer-side version of exactly the same idea:

If they do not genuinely need the information, do you genuinely need to give it to them?

Data that you never provide cannot later be exposed by that particular organisation in a breach, accidentally published by it, retained longer than expected or used for another purpose.

Three questions to ask before entering personal information

You do not need to read a twenty-page privacy policy every time you create an account. A quick three-question test is often enough.

The aim is not to become suspicious of every form. It is simply to stop treating every requested field as automatically necessary.

Which personal details do websites really need?

The answer depends on the service. The same information can be completely justified in one context and unnecessary in another.

Do they really need your exact date of birth?

Your date of birth is a good example because a service may genuinely need information about your age without necessarily needing the exact day, month and year you were born.

If a service needs to confirm that you are over 18, for example, the useful fact may simply be “this person is over 18”.

The European Data Protection Board has made this distinction explicitly in its work on age assurance. It notes that, depending on the purpose, a service may only need to know whether somebody is above or below an age threshold rather than receiving more detailed age-related data.

See: EDPB Statement on Age Assurance.

Of course, there are circumstances where an exact date of birth is genuinely required. Banking, insurance, healthcare, regulated identity verification and contractual processes are obvious examples.

The point is not “never provide your birthday”. It is:

Do not automatically provide a precise piece of personal information when a less precise answer would fulfil the same purpose.

So if a public-transport app needs to determine eligibility for an age-based fare, the request may make perfect sense. If an unrelated newsletter insists on your exact birthday merely to “complete your profile”, asking why is reasonable.

Your legal name is not always your username

There is an important difference between identity and display identity.

An airline ticket must normally correspond to the traveller's identity documents. A bank must know who its customer is. A contract may require the parties' correct legal names.

A discussion forum, gaming profile or community website is different. If its rules permit display names or pseudonyms, there may be no privacy benefit in publicly exposing your complete legal identity.

A pseudonym is not the same as anonymity. Information associated with a pseudonym can still be personal data if it can be linked back to a person. Both the AEPD and European Data Protection Board make that distinction clear.

See: AEPD guidance on pseudonymised data.

The practical rule is simpler: if a service only needs a name to display beside your posts, ask whether your passport name is really necessary.

Think before giving a website your main phone number

A phone number is not merely a way to receive calls.

For many people, the same mobile number remains with them for years and is used across messaging apps, online shops, financial services, deliveries, loyalty programmes, account recovery systems and two-factor authentication.

That makes a phone number useful as an identifier in practice. If the same number appears in several datasets, it can become one of the pieces of information that helps connect records relating to the same person.

Under European data-protection rules, information that identifies or can help identify an individual can constitute personal data. The European Commission also notes that multiple pieces of information which together identify somebody remain personal data.

See: European Commission — Data protection explained.

Before entering your number, ask what it will actually be used for

An online shop may reasonably want a phone number so a courier can contact you. A bank may use it for security or regulatory processes. A telecom provider obviously needs a telephone number to provide telephone service.

But if a newsletter, online quiz or simple forum asks for your mobile number, the reason may be much less obvious.

If the field is optional and you see no practical need for telephone contact, leaving it blank is often the simplest privacy decision.

Think about account security too

Phone numbers are also frequently used for SMS verification and account recovery. That can be convenient, but SMS is not always the strongest authentication method available.

ENISA's cyber-hygiene guidance recommends enabling two-factor authentication and, where there is a choice, preferring passkeys, security keys or authentication apps over codes sent by text message.

If you want to understand what someone could potentially do after obtaining your phone number, see Can Scammers Do Anything With Your Phone Number?

A secondary email address or alias can reduce unnecessary exposure

Your main email address can become another long-lived identifier, particularly if you use the same address for banking, shopping, social networks, newsletters, forums and dozens of minor registrations.

For services that do not need your primary address, a secondary email account or email-alias feature can create useful separation.

This is not only a consumer trick. The W3C's privacy principles explicitly discuss the privacy benefit of using a different email address in different contexts because it can reduce recognition across those contexts.

See: W3C Privacy Principles — Data Minimization.

An alias is particularly useful for shopping, newsletters, trial accounts and services where you still need to receive genuine messages but do not necessarily want to distribute your primary email address.

Avoid linking accounts simply because it is convenient

“Continue with Google”, “Sign in with Facebook” and similar options can be convenient and, when properly implemented, can also remove the need to create another password.

The privacy question is different: does this service need to become connected to another part of your digital identity?

Before linking accounts, look at what information will be shared and what permissions are being requested. If the connection gives you a real benefit, it may be worthwhile. If it merely saves a few seconds during registration, a separate account may provide cleaner separation.

The goal is not to avoid federated login at all costs. It is to avoid creating unnecessary links between services without thinking about them.

When should you not use false information?

Data minimisation is not advice to enter false information whenever possible.

There are many situations where accurate information is essential. These can include:

• banking and financial services;
• KYC and anti-money-laundering checks;
• government and public services;
• insurance;
• healthcare;
• contracts and legally significant transactions;
• airline and other identity-dependent travel bookings;
• age-restricted or otherwise regulated services;
• situations where correct details are required for delivery, billing or account recovery.

False information can also create very practical problems even when no law is involved. You may be unable to recover an account, prove that it belongs to you, receive a delivery or correct a booking. It may also breach the service's terms.

There is therefore an important difference between:

• not providing information that is optional;
• using a permitted display name or email alias; and
• deliberately giving false information where accurate identity is required.

The first two can be sensible privacy choices. The third can create consequences that have nothing to do with privacy.

A practical personal-data checklist

The next time a website or app asks you to complete a profile, try this:

ENISA includes limiting personal-information sharing among its basic cyber-hygiene practices and recommends thinking carefully about requests for personal information.

See: ENISA — Cyber Hygiene.

Why sharing less can also matter when scams reach you

Many scams become more convincing when the person contacting you already knows something real about you.

A caller who knows your name, phone number, employer or another genuine detail may sound more credible than a completely anonymous stranger. That does not mean every exposed detail automatically leads to fraud. It means that unnecessary personal information can create additional context that may later be used in social-engineering attempts.

If somebody unexpectedly claims to represent your bank or mobile operator, do not treat personal knowledge as proof of identity. Independently verify the organisation through a trusted contact channel.

Pingry has more detailed guides on this:

• How to Check if a Phone Number Is a Scam
• How to Check an Unknown Phone Number in Spain
• How to Tell if a Call Really Comes from Your Bank or Mobile Operator

How this connects to Pingry

Pingry is primarily concerned with phone-number information: helping people understand unknown calls and find verified official numbers for organisations in Spain.

But the same privacy principle applies.

Your phone number should not automatically be treated as harmless information simply because many websites ask for it. Before giving it away, it is worth considering whether the organisation genuinely needs that communication channel.

And when an unknown organisation calls you, independently checking the number can be preferable to confirming personal information simply because the caller asks for it.

You can search official organisational numbers in the Pingry verified phone-number directory for Spain.

The safest data may be the data you never shared

Password managers, passkeys, two-factor authentication, software updates and scam awareness are all important parts of cybersecurity.

But privacy has another layer that is much easier to overlook.

Every piece of personal information you provide creates another copy somewhere: in an account, a customer database, a mailing platform, a CRM, a support system or another service involved in processing it.

You cannot personally control the security of every organisation that holds your information. You can, however, sometimes control how much information reaches them in the first place.

Good cybersecurity isn't only about protecting the information you've already shared. Sometimes the safest personal data is the data you never needed to share in the first place.

Frequently asked questions

What is data minimisation?

Data minimisation is the principle that personal data should be adequate, relevant and limited to what is necessary for a specific purpose. Under the GDPR, organisations are responsible for applying this principle when processing personal data.

Should I give websites my real date of birth?

Provide your correct date of birth where it is genuinely required, such as regulated identity checks, banking, insurance or other services where accurate age or identity matters. If an unrelated service asks for your exact birthday without an obvious reason, check whether the field is optional or whether a less precise age answer is available.

Is it safe to use a fake name online?

A permitted display name or pseudonym can be appropriate where a service does not require legal identity. Do not provide false identity information where correct details are required for contracts, banking, government services, regulated checks, travel bookings or account ownership.

Should I give an online shop my phone number?

A shop may have a legitimate reason, such as delivery coordination or order notifications. If the number is optional and no telephone contact is necessary, you can consider leaving it blank.

Is a phone number personal data?

A phone number associated with an identifiable individual can be personal data. Because people often reuse the same mobile number across multiple services, it may also help link information about the same person across different records.

Are email aliases good for privacy?

They can be. Using separate aliases for different services can reduce unnecessary exposure of your primary address and make it harder to use one email address as a common identifier across unrelated contexts.

Should I avoid signing in with Google, Apple or Facebook?

Not necessarily. Federated login can be convenient and can have security advantages. The privacy question is whether you want the services linked and whether you are comfortable with the information and permissions involved.

What is the easiest way to share less personal data?

Start by leaving genuinely optional fields blank. Before providing additional information, ask why it is needed, what happens if you do not provide it and whether it genuinely needs to be accurate.

Sources and further reading

• European Commission — Principles of personal data processing under the GDPR
• AEPD — Protección de datos por defecto
• European Data Protection Board — Statement on Age Assurance
• ENISA — Cyber Hygiene
• European Commission — Data protection explained
• W3C — Privacy Principles: Data Minimization