| Document and Entity Information | Jun. 22, 2020 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001713683 |
| Document Type | 8-K |
| Document Period End Date | Jun. 22, 2020 |
| Entity Registrant Name | Zscaler, Inc. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-38413 |
| Entity Tax Identification Number | 26-1173892 |
| Entity Address, Address Line One | 120 Holger Way |
| Entity Address, City or Town | San Jose |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 95134 |
| City Area Code | (408) |
| Local Phone Number | 553-0288 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $0.001 Par Value |
| Trading Symbol | ZS |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
