21st Century Integrated Digital Experience Act or the 21st Century IDEA This bill requires an executive agency that maintains a website or digital service that is made available to the public to: eliminate or consolidate websites or web pages that are duplicative or overlapping; ensure that each public-facing website and digital service has a consistent appearance; ensure that each website, web-based form, and web-based application is accessible to individuals with disabilities; ensure that each website or digital service contains a search function that allows users to easily search content intended for public use; provide the website or digital service through an industry standard secure connection; ensure that each website or digital service is designed around user needs; and ensure that users of the website or digital service have the option for a more customized digital experience. Any agency website that is made available to the public after this bill's enactment shall be in compliance with website standards of the General Services Administration's Technology Transformation Services. Each agency shall make available to the public an online, mobile-friendly, digital service option for any in-person government transaction or paper-based process in a manner that decreases cost, increases digital conversion rates, and improves customer experience. Each agency shall submit to the Office of Management and Budget and Congress a plan to accelerate the use of electronic signature standards. Each agency's Chief Information Officer must meet specified requirements related to coordinating the customer experience and digital service delivery.