| Document And Entity Information | 12 Months Ended |
| Mar. 31, 2023 shares | |
| Document Information Line Items | |
| Entity Registrant Name | DESWELL INDUSTRIES, INC. |
| Trading Symbol | DSWL |
| Document Type | 20-F/A |
| Current Fiscal Year End Date | --03-31 |
| Entity Common Stock, Shares Outstanding | 15,935,239 |
| Amendment Flag | true |
| Amendment Description | This Amendment No. 1 (this “Amendment”) to the Annual Report on Form 20-F of Deswell Industries, Inc. (“Company,” “our,” “us,” or “we”) for the fiscal year ended March 31, 2023 filed on July 28, 2023 (the “Original Filing”) is being filed solely to amend and restate in its entirety Item 16I, “Disclosure Regarding Foreign Jurisdictions that Prevent Inspections” in order to provide the items required under Item 16I(a) of Form 20-F and to provide the disclosures under Item 16I(b) of Form 20-F.Except as noted above, this Amendment does not update or modify any disclosure in the Original Filing or reflect any event occurring after the filing of the Original Filing. Accordingly, this Amendment should be read in conjunction with the Original Filing.As required by Rule 12b-15 of the Securities and Exchange Act of 1934, as amended, we are filing or furnishing the certifications required under Section 302 and Section 906 of the Sarbanes-Oxley Act of 2002 as exhibits to this Amendment. |
| Entity Central Index Key | 0000946936 |
| Entity Current Reporting Status | Yes |
| Entity Voluntary Filers | No |
| Entity Filer Category | Non-accelerated Filer |
| Entity Well-known Seasoned Issuer | No |
| Document Period End Date | Mar. 31, 2023 |
| Document Fiscal Year Focus | 2023 |
| Document Fiscal Period Focus | FY |
| Entity Emerging Growth Company | false |
| Entity Shell Company | false |
| ICFR Auditor Attestation Flag | false |
| Document Registration Statement | false |
| Document Annual Report | true |
| Document Transition Report | false |
| Document Shell Company Report | false |
| Entity File Number | 001-33900 |
| Entity Incorporation, State or Country Code | D8 |
| Entity Address, Address Line One | 10B, Edificio Associacao Industrial De Macau |
| Entity Address, Address Line Two | 32 Rua do Comandante Mata e Oliveria |
| Entity Address, City or Town | Macao |
| Entity Address, Country | VG |
| Title of 12(b) Security | Common shares, no par value |
| Security Exchange Name | NASDAQ |
| Entity Interactive Data Current | No |
| Document Financial Statement Error Correction [Flag] | false |
| Document Accounting Standard | U.S. GAAP |
| Auditor Name | BDO China Shu Lun Pan Certified Public Accountants LLP |
| Auditor Location | People’s Republic of China |
| Auditor Firm ID | 1818 |
| Entity Address, Postal Zip Code | 0000 |
| Business Contact | |
| Document Information Line Items | |
| Contact Personnel Name | Herman Wong |
| Entity Address, Address Line One | 10B, Edificio Associacao Industrial De macau |
| Entity Address, Address Line Two | 32 Rua do Comandante Mata e Oliveira |
| Entity Address, City or Town | Macao |
| Entity Address, Country | VG |
| City Area Code | 853 |
| Local Phone Number | 28-322096 |
| Contact Personnel Email Address | hermanwong@jetcrown.net |
| Entity Address, Postal Zip Code | 0000 |
