Address Line 1 vs Address Line 2: What Goes in Each

Address line 1 is the street address: your house or building number plus the street name — 742 Evergreen Terrace. Address line 2 is the location inside that building — apartment, suite, unit, floor — and it’s optional. No apartment? Leave line 2 blank. Don’t write “N/A”, don’t repeat the street, don’t put your city there.

That’s the whole answer. The rest of this is the address line 1 vs address line 2 question in detail — what goes where, real examples, the one-line format, and how to build these fields correctly in your own forms. I’ve been shipping client forms since 2009, and address fields are still the ones checkouts get wrong most often.

Line 1 finds the building. Line 2 finds you inside it — and it stays optional.

What goes in address line 1

Address line 1 holds everything a delivery driver needs to find the building: the house or building number, the street name, and the street type (St, Ave, Blvd, Road). If your street has a directional, that goes here too — 350 N Main St, not just Main St.

Concrete examples:

• 742 Evergreen Terrace
• 1600 Amphitheatre Parkway
• 221B Baker Street (the B is part of the building number here, not a unit)
• PO Box 1042 (a PO box replaces the street address, so it lives in line 1)

One rule covers 95% of cases: if the information is needed to locate the building from the street, it belongs in line 1. Everything after the front door belongs in line 2.

What goes in address line 2

Address line 2 holds the unit designator: apartment, suite, floor, unit, room, or building letter within a complex. It exists because one street address can contain hundreds of separate mailboxes, and the carrier needs to know which one is yours.

Typical values:

• Apt 4B
• Suite 210
• Unit 12
• Floor 3
• Building C

What doesn’t go in line 2: your city, a landmark (“near the blue water tank”), delivery instructions (“ring twice”), or a second unrelated address. Instructions belong in a delivery-notes field if the form offers one. Cramming them into line 2 gets them printed onto a shipping label where nobody reads them as instructions.

Address line 2 is optional

If you live in a standalone house, address line 2 stays empty — and that’s the correct answer, not a mistake. Roughly two-thirds of the addresses I see in client submission data have no line-2 value at all. The field exists for the minority who need it.

This is the single biggest confusion with the field, from both sides:

Users invent filler. People type “N/A”, “None”, or repeat their street because an empty box feels wrong. All of that ends up printed on the label. If you don’t have a unit, leave it blank.

Form builders mark it required. I’ve audited checkouts where line 2 was a required field, forcing every house-dweller on the site to type garbage to proceed. Never make address line 2 required. There is no valid reason. If your validation rejects an empty line 2, your validation is wrong.

How to write an address on one line

To write an address on one line, run the pieces together in order, separated by commas: street address, unit, city, state, postal code. The unit slots in right after the street — exactly where line 2 would have gone.

742 Evergreen Terrace, Apt 4B, Springfield, IL 62704

Without a unit, drop that segment:

742 Evergreen Terrace, Springfield, IL 62704

USPS is fine with the unit on the same line as the street when it fits — USPS’s Publication 28 addressing standards treat 742 Evergreen Terrace Apt 4B as a valid single delivery line. The two-line split in forms is a data-entry convenience, not a postal requirement.

Address line 1 vs address line 2: examples

The fastest way to settle address line 1 vs address line 2 for your own address is to find your situation in a table:

Two of the six rows leave line 2 blank. That’s normal.

Designing address fields in your own forms

Building the address block yourself? Three decisions matter more than anything else: the labels, the autocomplete attributes, and keeping line 2 optional.

Label in plain language. “Street address” and “Apartment, suite, unit (optional)” outperform “Address line 1” and “Address line 2” — the generic labels are what causes the “N/A” filler in the first place. Put the word optional in the line-2 label itself, and pair every input with a visible label; the accessibility page covers why placeholder-only labels fail.

Set the autocomplete attributes. Browsers can fill the whole block in one click, but only if you tell them which field is which — MDN’s autocomplete reference lists every field name browsers understand:

<label>Street address
  <input type="text" name="address1" autocomplete="address-line1" required />
</label>
<label>Apartment, suite, unit (optional)
  <input type="text" name="address2" autocomplete="address-line2" />
</label>

Note the required on line 1 and its absence on line 2. That asymmetry is the whole point of this post in two attributes. If you write your forms in HTML — my case for skipping the builder covers why I do — this is a copy-paste. In Core Forms, the form templates give you a starting checkout block so you’re editing instead of typing from scratch.

Only collect an address when you ship something. A contact form doesn’t need one. Same logic as the GDPR consent pattern: every field you don’t collect is a field you don’t have to protect.

Where I’d do it differently: if your audience is heavily international, the US-style two-line split fights local formats (Japanese addresses, for one, invert the whole hierarchy). A single multi-line address field plus a country selector can beat line 1/line 2 there. For US and most European checkouts, the two-line pattern wins.

FAQ

What is address line 2?

Address line 2 is the optional second field in an address form for your unit inside a building: apartment number, suite, floor, unit, or building letter. It exists because one street address can hold many mailboxes. If your address has no unit — a standalone house, a PO box — leave it blank.

What do I put in address line 2 if I live in a house?

Nothing. Leave the field empty. A house address is complete with line 1, city, state, and ZIP. Don’t type “N/A” or “None” — whatever you enter gets printed on the shipping label, and filler text can confuse carriers or address-validation software. Blank is the correct value for most addresses.

Where does a PO box go, line 1 or line 2?

A PO box goes in address line 1, because it replaces the street address rather than refining it. Write PO Box 1042 in line 1 and leave line 2 blank. If a form asks for both a street address and a PO box, the PO box usually wins for mail delivery.

Where does “c/o” (care of) go?

Put the c/o line in address line 2 — c/o Marge Simpson — with the street address in line 1. Some carriers prefer c/o above the street line instead; both get delivered in practice. The key is keeping it out of the name field, where it breaks payment and identity matching.

Is there an address line 3?

Some forms offer an address line 3 for edge cases — a building name plus a unit plus a mailstop, common in campus and corporate addresses. Most people never need it. If a form only has two lines, combine the extras in line 2: Building C, Room 214 works fine as a single line.