| Cover | Dec. 31, 2019 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Dec. 31, 2019 |
| Entity Registrant Name | MITEK SYSTEMS INC |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-35231 |
| Entity Tax Identification Number | 87-0418827 |
| Entity Address, Address Line One | 600 B Street, Suite 100 |
| Entity Address, City or Town | San Diego, |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92101 |
| City Area Code | 619 |
| Local Phone Number | 269-6800 |
| 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 $0.001 per share |
| Trading Symbol | MITK |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000807863 |
| Amendment Flag | false |
