Одноразовый код нужен для подтверждения личности.

Одноразовый literally means single-use, one-time, or disposable, depending on context.

In this sentence, одноразовый код means a one-time code or single-use code.

A useful thing to know is that одноразовый is used both for physical objects and for things like passwords or codes:

• одноразовая посуда = disposable tableware
• одноразовый пароль = one-time password
• одноразовый код = one-time code

Because код is:

• masculine
• singular
• nominative case

The adjective has to agree with the noun, so одноразовый is the masculine singular nominative form.

Agreement in Russian means the adjective changes to match the noun’s:

• gender
• number
• case

For example:

• одноразовый код = masculine
• одноразовая ссылка = feminine
• одноразовое сообщение = neuter
• одноразовые коды = plural

Нужен is the short form of the adjective нужный.

In this sentence, нужен means is needed or is required.

So:

• нужный = needed/necessary, in its full form
• нужен = short form, commonly used as the predicate: is needed

Because the noun код is masculine singular, the short form is нужен.

Compare:

• Код нужен. = The code is needed.
• Ссылка нужна. = The link is needed.
• Подтверждение нужно. = The confirmation is needed.
• Документы нужны. = The documents are needed.

So нужен agrees with код.

Russian normally omits the verb "to be" in the present tense.

So where English says:

• The code is needed

Russian simply says:

• Код нужен

This is completely normal.

Russian does use forms of быть in the past and future:

• Код был нужен = The code was needed
• Код будет нужен = The code will be needed

But in the present tense, there is usually no separate word for is.

Because the preposition для always requires the genitive case.

The noun here is подтверждение (confirmation), and its genitive singular form is подтверждения.

So:

• для = for
• подтверждение = confirmation
• для подтверждения = for confirmation / for confirming

This is a very common pattern in Russian:

• для работы = for work
• для проверки = for checking
• для входа = for الدخول / for entering / for login
• для подтверждения = for confirmation

Личности is the genitive singular of личность.

Here it is used because подтверждение личности means confirmation of identity or identity verification.

So the structure is:

• подтверждение = confirmation
• личность = identity/personhood/personality, depending on context
• подтверждение личности = confirmation of identity

In English, we often say of identity. In Russian, that idea is commonly expressed with the genitive case.

So both nouns after для end up in genitive-related relationships:

• для подтверждения — genitive after для
• личности — genitive dependent on подтверждение

That is a very good question, because личность can be tricky.

Depending on context, личность can mean things like:

• personality
• individual
• identity

But in the set phrase подтверждение личности, it means identity verification or confirmation of identity.

This is a standard expression used in formal and technical contexts, especially online, in banking, security, and account access.

So in this sentence, you should understand личности as identity, not personality.

A fairly literal breakdown is:

• Одноразовый код = one-time code
• нужен = is needed
• для = for
• подтверждения личности = confirmation of identity

So very literally:

One-time code is needed for confirmation of identity.

More natural English would be:

• A one-time code is needed to verify your identity.
• A one-time code is required for identity verification.

Yes. Russian word order is flexible, because case endings show grammatical relationships.

The original sentence:

Одноразовый код нужен для подтверждения личности.

is neutral and natural.

You could also say:

Для подтверждения личности нужен одноразовый код.

This means the same thing, but it puts more emphasis on for identity verification.

Very roughly:

• Одноразовый код нужен... = focuses first on the code
• Для подтверждения личности нужен... = focuses first on the purpose

Both are correct.

Because код is the thing that is needed. It is the grammatical subject of the sentence.

In Код нужен, the noun that agrees with нужен is in the nominative:

• код — nominative singular
• нужен — masculine singular short form, agreeing with код

So even though English learners sometimes expect a different case after words meaning need, this sentence is built like:

The code is needed, not someone needs the code.

If you wanted to say I need the code, Russian would be structured differently:

• Мне нужен код.

There, код is still nominative, and мне marks the person who needs it.

Yes. A common alternative is необходим or необходимый, depending on structure.

For example:

• Одноразовый код необходим для подтверждения личности.

This sounds a bit more formal or official than нужен.

Very roughly:

• нужен = needed, required, common and natural
• необходим = necessary, more formal

In interface text, instructions, and system messages, both are possible, but нужен sounds straightforward and idiomatic.

Yes, very common.

This sentence sounds exactly like something you might see in:

• login screens
• banking apps
• account recovery pages
• two-factor authentication prompts
• identity verification forms

Russian often uses compact, formal phrasing in this kind of context, so sentences like this are worth learning as patterns:

• Код нужен для входа. = A code is needed to log in.
• Паспорт нужен для подтверждения личности. = A passport is needed for identity verification.
• Номер телефона нужен для регистрации. = A phone number is needed for registration.