Login vs Log In: Grammar for Tech Writing

Reviewed by the Grammarlyzer Editorial Team · Our Review Standards · Published January 22, 2026 · Updated June 13, 2026

Use the Right Form in UI and Documentation

📌 Quick Answer
Login is usually a noun or adjective. Log in is the verb phrase.

Memory Trick: If you can add "to" before it ("to log in"), use two words.

💡 Key Difference

Buttons can say "Login"; instructions should say "Log in to your account."

Quick Comparison

Form Use It For Quick Check
Login (one word) noun or adjective — a thing or a label 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.

The Tense Test Decides It Instantly

The fastest check is to change the time of the sentence. Only the verb can take a tense — so if you can say "logged in" or "logging in," you need the two-word verb. The noun never changes shape.

Sentence Can you change the tense? Use
Please ___ to continue. Yes → "I logged in to continue" log in
Enter your ___ details. No → "your logged-in details" ✗ 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.

"My ___ details" needs a noun/adjective, so one word. You can't say "my logging-in 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.

"___ screen" is the word describing a noun, so it's the one-word adjective — like "login page," "login button," "login form."

The Same Rule Across the Whole Family

sign in, log out, set up — all behave identically

The noun/adjective closes up; the verb stays open. "Create a signup" but "sign up now"; "the logout button" but "log out when done." Once you internalise login/log in, the rest follow automatically — see setup vs set up.

The hyphen "log-in" is an older adjective style

You'll see log-in (hyphenated) as an adjective in some British and older style guides: "log-in credentials." Modern product writing has mostly settled on the closed "login" for the noun and adjective, so prefer that unless a house style says otherwise.

Why this matters in UI copy

Buttons and links are where this shows up most. A button that performs the action reads "Log in"; a heading naming the screen reads "Login." Mixing them ("Login to your account") is the single most common microcopy slip in apps.

🎯 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.

See It Live: Our Engine Flags a Real Mistake

The example below isn't static. Grammarlyzer's engine analyses it on this page and flags what it finds. The starter sentence (“I forgot my log in details.”) already contains a slip—edit it or paste your own to watch the engine react.

Expected correction: "I forgot my login details.".

Honest limits: the engine flags the spacing, but login (a noun) versus log in (a verb) depends on how you use it in the sentence. Decide noun or verb first, then trust the check.

Frequently Asked Questions

Why do apps use "Login" on buttons?

UI labels often use noun-style wording for brevity.

Is "log into" acceptable?

Many teams use it, but strict grammar prefers "log in to."

Deep Dive

Think in two buckets: this is a noun phrase when naming a label, and a verb phrase when describing an action.

Most errors happen when teams write one style in copy and another in instructions. Security and auth pages are especially sensitive to this distinction.

Practical Use Cases

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

Context How to Choose
UI label Short labels often use the noun/adjective form: "Login page" or "Login attempt."
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.

Why This Mistake Happens

The confusion happens because software buttons often shorten instructions. A button may say "Login," but the sentence around it still needs the verb phrase "log in."

Mini Checklist

  • If you can put "to" before it, write "log in."
  • If it names a screen, session, field, or attempt, write "login."
  • For strict style, write "log in to" when "in" belongs to the verb phrase.

How Grammarlyzer Can Help

Grammarlyzer can help catch word-form issues in surrounding sentences. Product teams should still follow their own UI style guide for button labels.

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

Related Articles

Login vs Log In Across Tech and Professional Contexts

In product and interface writing, the two forms serve entirely different functions and must be used correctly for both grammatical accuracy and user experience clarity. When a button label says "Login," users understand it as the name of an action or destination screen — a noun label. But in the instruction text beneath the same button, you must write "Log in with your email to continue," using the verb phrase. Mixing forms in a single screen — "Click Login to login" — creates a subtle inconsistency that trained writers notice immediately and that can make a product's copy feel unprofessional. Most design systems and content style guides from major tech companies (including Google's Material Design guidelines and Microsoft's writing guidelines) explicitly distinguish the noun from the verb.

In technical documentation and help articles, the verb "log in" appears frequently in step-by-step instructions where users are told to perform an action: "Step 1: Log in to your account. Step 2: Navigate to Settings." The noun "login" appears when naming the object of the action: "Your login credentials will be sent to your email" or "A failed login attempt triggers a security alert." Academic papers that discuss authentication systems follow the same pattern: the systems section might describe "a two-factor login process" (noun modifier before a noun) and later describe how "users log in using biometric data" (verb phrase in a procedural description). Both forms are correct — the sentence role determines the form.

In casual and business writing, the most frequent error is using the one-word noun "login" as a verb in instructions and action language. This pattern appears most commonly in informal business emails: "Please login before 9 a.m. to access the webinar" — which should read "Please log in before 9 a.m." The noun form in a verb position is the equivalent of writing "Please access your account-access before 9 a.m." — grammatically awkward when you parse it carefully, even if the meaning is clear in context. Building the habit of asking "is this an action or a thing?" before writing either form resolves the ambiguity in every situation.

The "To" Infinitive Test

Try placing "to" immediately before the word. If it sounds like an instruction — "to log in" — you need the two-word verb. If "to" sounds wrong or awkward — "to login" feels odd when you think about it — you are likely working with the noun. This test works because infinitives take verbs, not nouns. "To login" would be like writing "to access-attempt," which no one would accept.

Proofreading Questions About Login vs Log In

What about "log into" vs "log in to"?

This is a secondary distinction that trips up careful writers. In strict grammar, "log in" is the phrasal verb and "to" introduces the destination or purpose: "Log in to your account" keeps "log in" intact as the verb and "to your account" as the prepositional phrase. "Log into" merges the "in" with "to" into a single preposition, which technically detaches "in" from the verb phrase. Many editors and style guides accept "log into" in informal writing and acknowledge that the distinction is fading, but formal technical documentation — particularly government, medical, and financial sector writing — still prefers "log in to" to preserve the grammatical structure of the phrasal verb.

Why do apps label buttons "Login" instead of "Log In"?

UI buttons and navigation labels operate under different conventions than prose writing. Buttons are labels — abbreviated signposts — not instructions, so the noun form "Login" works as a compact, recognizable label for the authentication screen or action. Some apps do use "Log In" on buttons to signal the action more explicitly, and both are widely used and understood. The key is consistency within a single product: if your homepage button says "Login," your confirmation message should not say "You have successfully logged in to your account" and then later refer to "your log in history." Pick a consistent style across all touchpoints.

How should I handle "logout" and "log out" by the same logic?

The exact same rule applies: "logout" is the noun or adjective form, while "log out" is the verb phrase. "Click the logout button" uses the noun as an adjective modifying "button." "Please log out of your session when you are finished" uses the verb phrase. The parallel is so consistent that once you learn either pair — login/log in or logout/log out — you have effectively learned the rule for both. Other pairs following the same pattern include signup/sign up, signin/sign in (less common), and checkout/check out in e-commerce contexts.

Does capitalization change anything for "login" vs "log in"?

Capitalization is a separate question from word spacing but is worth addressing. When "Login" appears as the title of a screen or as a proper label in a user interface, it is often capitalized regardless of whether it is the noun or verb form. In body text and instructions, standard sentence-case capitalization applies: capitalize "login" only when it begins a sentence or is part of a proper name (such as "the Login page"). The word spacing rule — one word for the noun, two words for the verb — stays constant regardless of capitalization, so you can resolve the noun/verb question first, then apply your document's capitalization conventions.

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