| Cover Page | Aug. 05, 2021 | Nov. 05, 2020 |
| Cover [Abstract] | ||
| Document Type | 8-K | |
| Document Period End Date | Aug. 5, 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 | 4637 NW 18th Avenue | |
| Entity Address, City or Town | Camas | |
| Entity Address, State or Province | WA | |
| Entity Address, Postal Zip Code | 98665 | 98607 |
| 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 |
