| Cover | May 11, 2023 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | May 11, 2023 |
| Entity Registrant Name | Janus International Group, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-40456 |
| Entity Tax Identification Number | 86-1476200 |
| Entity Address, Address Line One | 135 Janus International Blvd. |
| Entity Address, City or Town | Temple |
| Entity Address, State or Province | GA |
| Entity Address, Postal Zip Code | 30179 |
| City Area Code | 866 |
| Local Phone Number | 562-2580 |
| 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 | JBI |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | true |
| Entity Ex Transition Period | false |
| Entity Central Index Key | 0001839839 |
| Amendment Flag | false |
