Login vs Log In: Grammar for Tech Writing

Reviewed by the Grammarlyzer Editorial Team · Our Review Standards · Published January 22, 2026 · Updated July 16, 2026

Separate the noun from the verb, then apply the product’s terminology

📌 Quick Answer
Login is a noun: “your login,” “a failed login,” or “the login page.” Log in is the verb: “Log in to continue” or “She logged in yesterday.”

Two tests: If the phrase changes to logged in or logging in, it is the two-word verb. If an article or possessive fits before it, as in a login or your login, it is the noun.

💡 Key Difference

When a control directly performs the action, Log in is the grammatical verb label. Login can name a destination, process, or credential. Product terminology can override the pair entirely; Microsoft style recommends Sign in.

Quick Comparison

Form Use It For Quick Check
Login (one word) noun, including a noun used before another noun Put the/a/your in front: your login, the login page.
Log in (two words) the verb — an action Change the tense: logged in, logging in → it's the verb.

Use Role and Tense Together

Change the time of an action to expose the verb: log in, logged in, and logging in stay open. For the noun, test an article or possessive: a login, the login, and your login. Before another noun, login can work as a noun modifier, as in login page or login attempt.

Sentence Can you change the tense? Use
Please ___ to continue. Yes → "I logged in to continue" log in
Enter your ___ details. Your calls for a noun or noun modifier login
The ___ page is down. No → it labels "page" login

Common Mistakes

❌ Incorrect:

"Please login to continue."

✓ Correct:

"Please log in to continue."

You need the verb phrase in action instructions.
❌ Incorrect:

I forgot my log in details.

✓ Correct:

I forgot my login details.

After my, the phrase needs a noun or noun modifier. The closed noun login labels the details.
❌ Incorrect:

I login every morning to check messages.

✓ Correct:

I log in every morning to check messages.

This is an action you repeat — a verb — so two words. Tense test: "I logged in yesterday" confirms it.
❌ Incorrect:

Click here to access the log in screen.

✓ Correct:

Click here to access the login screen.

Login is a noun used to label another noun here, as in login page, login button, and login form.

Dictionary Rule and Product Style Are Different Layers

What dictionaries record

Cambridge lists login as a noun for a name, an act of entering a system, or a place on a screen. Merriam-Webster lists log in as a verb variant of log on and gives its tense forms as logged in and logging in.

Log in to and log into are both recorded

The Merriam-Webster entry gives log in to the mainframe and notes that log into is also written. Use log in to when you want to keep the two-word verb visually explicit, but do not label log into universally ungrammatical.

A product style may choose Sign in

Microsoft’s style guide recommends sign in and sign out, and says not to use log in or login unless those terms appear in the interface being documented. That is a product-language decision, not a contradiction of the dictionary forms.

🎯 Test Your Knowledge

1. You must ___ before checkout.

2. Your ___ attempt failed.

3. I'll ___ later to review the report.

4. The ___ form needs an email and password.

5. Users who ___ daily see more updates.

Try It Live: Login or Log In?

The exact starter sentence was tested in the local browser build on July 16, 2026. The engine did mark text, but it treated in details as the phrase to change and suggested in detail. It did not propose the contextually correct noun login.

Context-based revision: "I forgot my login details."

The revision with login details returned no issues in the same test. This result demonstrates a wrong-target suggestion for one exact input; it does not establish how the engine handles every noun-versus-verb sentence.

Frequently Asked Questions

Is "login" a noun or a verb?

Cambridge lists login as a noun for a name, an act of entering a system, or a place on a screen. Use the two-word log in when you need the verb: "Users log in with a passkey."

Should a button say "Login" or "Log in"?

If the label directly performs the action and the product uses log terminology, Log in is the verb form. Login can name a destination or process, as in "Login help." A product style guide may instead require Sign in.

Is "log into" acceptable?

Yes. Merriam-Webster records both log in to and log into. Log in to keeps the two-word verb visible, but log into is an established written variant. Follow the relevant house style.

Is the hyphenated form "log-in" accepted?

Yes. Cambridge gives log-in as an alternative noun spelling, and Merriam-Webster records the hyphenated noun. This guide uses the closed noun login consistently unless quoted UI or a house style requires another form.

What did the Grammarlyzer checker do with the login example?

On July 16, 2026, the exact seed "I forgot my log in details." triggered an unrelated usage suggestion that changed "in details" to "in detail"; it did not propose login. The revision "I forgot my login details." returned no issues.

Deep Dive

Login (one word) is a noun. Write "your login," "the login page," and "a failed login attempt." In the last two examples, the noun is used before another noun to identify its type.

Log in (two words) is a phrasal verb: it describes an action. Write "please log in to continue," "users who log in daily," "she logged in this morning" — anywhere you need a verb that can change tense.

The sentence role controls the spacing. Please login places the noun where an action verb is needed; the log in page separates a noun label that the dictionary records as login.

Practical Use Cases

This pair matters in product copy, help docs, emails from support teams, and security instructions.

Context How to Choose
UI label Name a destination with the noun login, or label an action Log in. Match the product's navigation model and terminology.
Instruction Use the verb phrase for an action: "Log in to your account before downloading the file."
Technical writing Keep terms consistent across one document so users do not wonder whether two actions are different.

Three Layers to Check in Product Copy

Grammar: choose the noun login or the verb log in. Interface role: decide whether a label names a destination or triggers an action. House style: check whether the product uses log in, sign in, or a branded term. Keeping these layers separate prevents a style preference from being presented as a universal grammar rule.

Mini Checklist

  • If the phrase changes to logged in or logging in, use the two-word verb.
  • If an article or possessive fits, or the word labels another noun, test the noun login.
  • Choose between log in to, log into, and sign in to from the relevant house style; do not invent a universal ban.

What the Checker Test Adds

The exact seed shows that a diagnostic can target the wrong phrase even when it marks nearby text. Product teams should verify the sentence role and their UI terminology instead of accepting the first replacement automatically.

You can compare this rule with Into vs In To and Setup vs Set Up.

Related Articles

A Manual Audit for One Screen or Document

  1. Inventory every form. Search for login, log in, log-in, log into, and any sign in variants.
  2. Mark the grammatical job. Use login for a noun or noun label and log in for an action, including tense forms such as logged in.
  3. Classify the interface role. A page title can name a destination; a button can perform an action. Do not assume that one label works for both roles.
  4. Apply the house terminology. If the product standard says Sign in, update the cluster consistently instead of mixing two authentication vocabularies.
  5. Review automated suggestions in context. Reject replacements that repair a nearby phrase while leaving the intended noun-versus-verb decision unresolved.

Do not confuse grammar with terminology

Login versus log in is a noun-versus-verb choice. Log in versus sign in is usually a product-language choice. A reliable audit checks both.

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