You need to sign-in (sign in) somewhere

Use "sign in" (no hyphen) for the action. Use "sign-in" (with a hyphen) when the phrase names something or modifies a noun, as in a label or compound adjective: the sign-in page.

Fast rule

Action = sign in (no hyphen). Noun/adjective = sign-in (hyphen).

Verb: You need to sign in to continue. - no hyphen.
Noun/adjective: Click the sign-in button. The sign-in process. - hyphen.
If you can replace the phrase with a single verb (e.g., "log in"), treat it as a verb (no hyphen).

Core explanation: verb vs noun/adjective

Phrasal verbs pair a verb and a particle. When they describe an action, keep them open: sign in. When they name a thing (a process, page, button) or modify a noun directly, writers often hyphenate: sign-in.

Quick test: if the phrase answers "What do you do?" it's a verb. If it answers "What is it?" or sits before a noun as a modifier, hyphenate.

Action (no hyphen): Please sign in now.
Label/modifier (hyphen): Use the sign-in form.
Wrong: You need to sign-in to submit the form.
Right: You need to sign in to submit the form.

Hyphenation rules (grammar, brief)

Hyphenate when the phrase has been nominalized (used as a noun) or when it acts as a compound adjective before another noun. Do not hyphenate when it functions as the main verb or part of the predicate.

Note: some compounds close up (login, setup) as nouns in many style guides; check a dictionary or your house style if unsure.

Verb: She will sign in at 9 a.m. - no hyphen.
Noun: The sign-in was fast. - hyphen (or sometimes a closed form depending on style).
Adjective before noun: the sign-in page - hyphen to bind the words.
Wrong: Open the sign in page to create an account.
Right: Open the sign-in page to create an account.

Spacing, punctuation & UI copy

Short action labels and buttons should use the verb form: "Sign in" (no hyphen). Labels that name elements use the hyphen: "Sign-in settings", "Sign-in page". Do not add spaces around hyphens.

Button text (action): Sign in
Label (noun/adjective): Sign-in button / Sign-in form
No spaces: sign-in (not sign - in)
Wrong: Sign-in - for a button that performs the action.
Right: Sign in - for a button that performs the action.
Right: Sign-in form - for a label that names the element.

Work examples (copy-ready)

Use the verb form in instructions; hyphenate when naming UI elements, procedures, or documents.

Work - Wrong: You need to sign-in to access the timesheet.
Work - Right: You need to sign in to access the timesheet.
Work - Wrong: The sign in procedure is outlined in the manual.
Work - Right: The sign-in procedure is outlined in the manual.
Work - Wrong: Please use the sign in link in the company portal.
Work - Right: Please use the sign-in link in the company portal.

School examples (copy-ready)

For handouts and signage, pick the form that matches function: action or label.

School - Wrong: Students must sign-in to turn in assignments.
School - Right: Students must sign in to turn in assignments.
School - Wrong: The sign in sheet will be at the front.
School - Right: The sign-in sheet will be at the front.
School - Wrong: You need to sign-in before starting the test.
School - Right: You need to sign in before starting the test.

Try your own sentence

Test the whole sentence in context. The sentence usually reveals whether the phrase is acting as a verb or a label.

Casual examples (messages, chat, invitations)

Casual copy typically uses the verb form; only hyphenate when naming an object or page.

Casual - Wrong: Hey, sign-in when you get here.
Casual - Right: Hey, sign in when you get here.
Casual - Wrong: Use the sign in button to continue.
Casual - Right: Use the sign-in button to continue.
Casual - Wrong: Don't forget to sign-in before the meeting.
Casual - Right: Don't forget to sign in before the meeting.

More wrong/right pairs + quick rewrites

Train your eye with these pairs. When a phrase names a thing, hyphenate or use the noun form as appropriate.

Wrong: You need to login to your account.
Right: You need to log in to your account.
Wrong: Please follow-up with the client.
Right: Please follow up with the client.
Wrong: Open the sign in dialog and pick a domain.
Right: Open the sign-in dialog and pick a domain.
Wrong: Set-up the workspace before the workshop.
Right: Set up the workspace before the workshop.
Wrong: Drop off the pickup at the desk.
Right: Drop off the pick-up at the desk. (Or use "pickup" as a noun: the pickup is at the desk.)

Rewrite help: quick templates

Use the 3-step checklist: identify the phrase's function → decide hyphenation → apply or rewrite for clarity.

Checklist: 1) Is it an action? 2) Does it name a thing or modify a noun? 3) If unsure, rewrite to avoid ambiguity.
Verb template: [Subject] need(s) to sign in to [do X].
Label template: the sign-in [page/button/form/process]

Rewrite:
Original: You need to sign-in somewhere. → You need to sign in at the front desk.
Rewrite:
Original: Click sign-in link. → Click the sign-in link to continue.
Rewrite:
Original: Sign-in required. → Signing in is required to access this feature.

Memory trick & short heuristics

Memory trick: can you replace the phrase with a single verb (like "log in")? If yes, it's a verb - no hyphen. If you can insert "page", "button", or "form" after it, it's likely a label - hyphenate.

Swap test: "You need to ___" - if the blank takes a verb, use two words.
Noun test: "the ___ page" - if the blank names an element, hyphenate.
When unsure, rewrite: "Signing in is required" avoids hyphenation errors.
Usage: "You need to sign in" (action) vs "the sign-in page" (label).

Similar mistakes to watch for

Apply the same tests to other phrasal verbs: log in/login, set up/setup, follow up/follow-up, check in/check-in, pick up/pickup. Some nouns close up; others use hyphens depending on style.

log in (verb) → login (noun/adjective): "Please log in." vs "the login page".
set up (verb) → setup (noun): "Set up your account." vs "the setup guide".
follow up (verb) → follow-up (noun/adjective): "Please follow up." vs "a follow-up email".
Wrong: You need to login to your account.
Right: You need to log in to your account.

FAQ

Should I use "sign-in" on a button that performs the action?

No. Buttons perform actions, so use "Sign in" (no hyphen). Reserve "sign-in" for labels that name elements (sign-in page, sign-in form).

Is "login" the same as "sign in"?

"Login" is typically a noun/adjective (the login page). "Log in" is the verb. For "sign in", the verb stays as two words; the noun/adjective often appears as "sign-in" in many style guides.

Can I just hyphenate when I'm unsure?

Hyphenating a verb looks wrong. If unsure, rewrite: use "Signing in is required" or "Please sign in" to avoid wrong hyphenation.

How can I fix many instances quickly in a document?

Search for "sign-" and "sign in" occurrences and apply the verb vs noun/adjective test. Use find-and-replace only after checking each match; automation helps, but review suggestions manually.

Will grammar checkers catch these errors reliably?

Most grammar checkers flag likely incorrect hyphenation and suggest fixes, but always confirm the suggestion matches the sentence function (action vs label).

Quick sanity check

Paste a sentence into a grammar tool or run the swap test: if the phrase fills a verb slot, keep it open; if it names an element, hyphenate. Choose a consistent approach in your document or product style guide and apply it everywhere.