| Document and Entity Information | Oct. 25, 2019 |
| Cover [Abstract] | |
| Amendment Flag | true |
| Entity Central Index Key | 0000704532 |
| Document Type | 8-K/A |
| Document Period End Date | Oct. 25, 2019 |
| Entity Registrant Name | ONTO INNOVATION INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-39110 |
| Entity Tax Identification Number | 94-2276314 |
| Entity Address, Address Line One | 16 Jonspin Road |
| Entity Address, City or Town | Wilmington |
| Entity Address, State or Province | MA |
| Entity Address, Postal Zip Code | 01887 |
| City Area Code | 978 |
| Local Phone Number | 253-6200 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Stock, $0.001 par value per share |
| Trading Symbol | ONTO |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
| Amendment Description | On October 28, 2019, Onto Innovation Inc. (“Onto Innovation”) filed with the Securities and Exchange Commission (the “SEC”) a Current Report on Form 8-K (the “Initial Form 8-K”) disclosing that on October 25, 2019, pursuant to an Agreement and Plan of Merger, dated as of June 23, 2019, with Rudolph Technologies, Inc., a Delaware corporation (“Rudolph”), and PV Equipment Inc., a Delaware corporation and a direct wholly-owned subsidiary of Nanometrics (“Merger Sub”), Merger Sub merged with and into Rudolph, with Rudolph continuing as the surviving corporation and a direct wholly-owned subsidiary of Onto Innovation (the “Merger”). In the Initial Form 8-K, Onto Innovation stated its intention to file the historical financial statements of Rudolph and the pro forma financial information required by parts (a) and (b) of Item 9.01 of Form 8-K not later than 71 calendar days after the date that the Initial Form 8-K was required to be filed with the SEC. Pursuant to the instructions to Item 9.01 of Form 8-K, this Amendment No. 1 to Current Report on Form 8-K/A amends the Initial 8-K in order to provide the required financial information. |
