Can you lose your green card by living abroad?

This is the part people get backwards. There is no rule saying "179 days is safe and 181 is not". USCIS describes loss of status as remaining outside the United States for an extended period unless it is a temporary absence, shown by the reason for the trip, how long you planned to be absent, the circumstances, and anything that prolonged it.

That makes it an evidence question. Continuing US employment, family remaining in the US, a home you kept, tax returns filed as a resident, accounts and licences maintained — these are what make an absence look temporary. Their absence is what makes it look like a move.

The widely-quoted six-month and one-year figures are real, but they are practical thresholds rather than a statutory allowance: longer absences attract questions at the border, and a re-entry permit exists precisely because a long trip needs explaining in advance.

For naturalisation, the numbers are exact, and this is where a long trip does the most quantifiable damage:

• More than 6 months but less than 1 year — presumed to break continuous residence. Rebuttable, with evidence such as uninterrupted US employment, immediate family in the US, or a US home you kept access to.
• 1 year or more — automatically breaks continuity. This one cannot be argued away with evidence, though qualifying employment abroad can preserve residence via an approved Form N-470.

So a ten-month absence and a thirteen-month absence sit on opposite sides of a wall: one is an argument you can win, the other is not.

If you know a long absence is coming, Form I-131 is the instrument. Two features matter for planning: it must be applied for while you are physically present in the United States, and it is intended for absences beyond a year rather than as a routine formality.

It does not make an absence temporary by itself — it is evidence that you planned for it to be — and it does not stop the naturalisation clock rules above from applying.

A single long trip is assessed twice, and people usually think about only one:

• Do you still hold the status? Intent and circumstances, no fixed number.
• Are you still on track to naturalise? Fixed numbers, applied to each single absence.

Because the second is arithmetic, it is the one a day-level record answers outright — and the same record is the raw material for the evidence the first test asks for.

Anything close to either line is worth taking proper advice on before booking, not after returning.

• USCIS — Maintaining permanent residence
• USCIS — Policy Manual, Volume 12 Part D Chapter 3: Continuous Residence
• USCIS — Form I-131, Application for Travel Document