| Cover Page | Mar. 03, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Mar. 3, 2021 |
| Entity Registrant Name | NLIGHT, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-38462 |
| Entity Tax Identification Number | 91-2066376 |
| Entity Address, Address Line One | 5408 NE 88th Street, Building E |
| Entity Address, City or Town | Vancouver |
| Entity Address, State or Province | WA |
| Entity Address, Postal Zip Code | 98665 |
| City Area Code | 360 |
| Local Phone Number | 566-4460 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, par value $0.0001 per share |
| Trading Symbol | LASR |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001124796 |
