Cybersecurity Risk Management and Strategy Disclosure	12 Months Ended
Dec. 31, 2025
Cybersecurity Risk Management, Strategy, and Governance [Line Items]
Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block]	Cybersecurity risk management, which involves resource commitments and management attention, is overseen both as a critical component of our overall risk management program and as a standalone program. We have implemented a risk-based, cross-functional approach to identifying, preventing, and mitigating cybersecurity threats and incidents, while also implementing controls and procedures that provide for the prompt escalation of certain cybersecurity incidents. Our cybersecurity program uses a layered strategy, relying on technology and human processes to safeguard our client’s data. We embed controls within our business processes and technology development, starting with design and engineering and extending to operations. Our defense-in-depth strategy utilizes numerous layers of security controls, processes, and procedures across our information systems and networks, including but not limited to, vulnerability management, multi-factor authentication (MFA), identity access management (IAM), privileged access management (PAM), endpoint security, mobile security, application security, encryption, network security, cloud security, web security, and event monitoring and logging. Aspects of our program undergo several annual independent third-party audits and reviews, and are part of continuous bug bounty and responsible disclosure programs. We regularly review and update our cybersecurity program to address emerging threats and maintain alignment with industry best practices. We maintain a written Information Security Policy, which establishes the foundational components of our cybersecurity program and our high-level security responsibilities over all technologies, facilities and data. When engaging service providers and third-party vendors, we perform due diligence to assess whether these providers have appropriate privacy and security controls, and we generally require these providers to implement appropriate protective measures, and to use confidential information solely for the purposes of performing their services. Additionally, we have adopted a documented Incident Response Plan that applies in the event of a cybersecurity incident to provide a standardized framework for response. Our incident response process generally follows the NIST 800-61 framework and focuses on four phases: preparation; detection and analysis; containment, eradication and recovery; and post-incident remediation. We have implemented a security training and awareness program for all Gartner employees and third-party contractors. Employees receive security training in connection with onboarding as well as annual awareness and training activities throughout their employment. Further, Gartner carries cybersecurity insurance covering the company and its subsidiaries. Material Cybersecurity Risks, Threats & Incidents. While we have not experienced any material cybersecurity threats or incidents, there can be no guarantee that we will not be the subject of future successful attacks, threats or incidents. Additional information on cybersecurity risks we face can be found in Part I, Item 1A “Risk Factors” of this Report under the heading “Strategic and Operational Risks – We are exposed to risks related to cybersecurity,” which should be read in conjunction with the foregoing information.
Cybersecurity Risk Management Processes Integrated [Flag]	true
Cybersecurity Risk Management Processes Integrated [Text Block]	Cybersecurity risk management, which involves resource commitments and management attention, is overseen both as a critical component of our overall risk management program and as a standalone program. We have implemented a risk-based, cross-functional approach to identifying, preventing, and mitigating cybersecurity threats and incidents, while also implementing controls and procedures that provide for the prompt escalation of certain cybersecurity incidents.
Cybersecurity Risk Management Third Party Engaged [Flag]	true
Cybersecurity Risk Third Party Oversight and Identification Processes [Flag]	true
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag]	false
Cybersecurity Risk Board of Directors Oversight [Text Block]	The Audit Committee has the primary responsibility of assisting our Board of Directors in overseeing risks related to cybersecurity matters. The Board and the Audit Committee receive quarterly cybersecurity-related reports from our Chief Information Officer (“CIO”), that address several topics, including cybersecurity strategy, the threat environment, the status of ongoing information security program initiatives, and information security program metrics. Additionally, we have documented protocols by which certain cybersecurity incidents that meet established reporting thresholds are escalated within the Company and, where appropriate, reported to the Board and/or the Audit Committee. At the management level, our CIO, who reports directly to the CEO, has over 20 years of experience serving in IT management, software development, and technology-based roles across a variety of industries, including publishing, media and entertainment, and financial and insurance services. Our Chief Information Security Officer (“CISO”), who reports directly to the CIO, has extensive cybersecurity knowledge and skills gained from over 25 years of work experience serving in executive security roles and in a variety of industries such as telecommunications, enterprise service companies, and healthcare. Our CISO is responsible for understanding, managing, and communicating cybersecurity risk internally to our management, and works closely with our Legal & Compliance team to oversee compliance with legal, regulatory, and contractual security requirements. Our CISO heads the Information Security Team, which is responsible for implementing, monitoring, and maintaining cybersecurity and data protection practices across our business. The Information Security Team covers a wide range of cyber and information security responsibilities. Our CISO also receives reports on cybersecurity threats on an ongoing basis and regularly reviews risk management measures implemented by the Company to identify and mitigate cybersecurity risks. In addition to our internal capabilities, we also engage external consultants, legal counsel, or other third-party advisors to assist with assessing, identifying, and managing cybersecurity risks.
Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block]	The Audit Committee has the primary responsibility of assisting our Board of Directors in overseeing risks related to cybersecurity matters.
Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block]	The Audit Committee has the primary responsibility of assisting our Board of Directors in overseeing risks related to cybersecurity matters. The Board and the Audit Committee receive quarterly cybersecurity-related reports from our Chief Information Officer (“CIO”), that address several topics, including cybersecurity strategy, the threat environment, the status of ongoing information security program initiatives, and information security program metrics. Additionally, we have documented protocols by which certain cybersecurity incidents that meet established reporting thresholds are escalated within the Company and, where appropriate, reported to the Board and/or the Audit Committee. At the management level, our CIO, who reports directly to the CEO, has over 20 years of experience serving in IT management, software development, and technology-based roles across a variety of industries, including publishing, media and entertainment, and financial and insurance services. Our Chief Information Security Officer (“CISO”), who reports directly to the CIO, has extensive cybersecurity knowledge and skills gained from over 25 years of work experience serving in executive security roles and in a variety of industries such as telecommunications, enterprise service companies, and healthcare. Our CISO is responsible for understanding, managing, and communicating cybersecurity risk internally to our management, and works closely with our Legal & Compliance team to oversee compliance with legal, regulatory, and contractual security requirements.
Cybersecurity Risk Role of Management [Text Block]	The Audit Committee has the primary responsibility of assisting our Board of Directors in overseeing risks related to cybersecurity matters. The Board and the Audit Committee receive quarterly cybersecurity-related reports from our Chief Information Officer (“CIO”), that address several topics, including cybersecurity strategy, the threat environment, the status of ongoing information security program initiatives, and information security program metrics. Additionally, we have documented protocols by which certain cybersecurity incidents that meet established reporting thresholds are escalated within the Company and, where appropriate, reported to the Board and/or the Audit Committee. At the management level, our CIO, who reports directly to the CEO, has over 20 years of experience serving in IT management, software development, and technology-based roles across a variety of industries, including publishing, media and entertainment, and financial and insurance services. Our Chief Information Security Officer (“CISO”), who reports directly to the CIO, has extensive cybersecurity knowledge and skills gained from over 25 years of work experience serving in executive security roles and in a variety of industries such as telecommunications, enterprise service companies, and healthcare. Our CISO is responsible for understanding, managing, and communicating cybersecurity risk internally to our management, and works closely with our Legal & Compliance team to oversee compliance with legal, regulatory, and contractual security requirements. Our CISO heads the Information Security Team, which is responsible for implementing, monitoring, and maintaining cybersecurity and data protection practices across our business. The Information Security Team covers a wide range of cyber and information security responsibilities. Our CISO also receives reports on cybersecurity threats on an ongoing basis and regularly reviews risk management measures implemented by the Company to identify and mitigate cybersecurity risks. In addition to our internal capabilities, we also engage external consultants, legal counsel, or other third-party advisors to assist with assessing, identifying, and managing cybersecurity risks.
Cybersecurity Risk Management Positions or Committees Responsible [Flag]	true
Cybersecurity Risk Management Positions or Committees Responsible [Text Block]	The Audit Committee has the primary responsibility of assisting our Board of Directors in overseeing risks related to cybersecurity matters. The Board and the Audit Committee receive quarterly cybersecurity-related reports from our Chief Information Officer (“CIO”), that address several topics, including cybersecurity strategy, the threat environment, the status of ongoing information security program initiatives, and information security program metrics. Additionally, we have documented protocols by which certain cybersecurity incidents that meet established reporting thresholds are escalated within the Company and, where appropriate, reported to the Board and/or the Audit Committee.
Cybersecurity Risk Management Expertise of Management Responsible [Text Block]	At the management level, our CIO, who reports directly to the CEO, has over 20 years of experience serving in IT management, software development, and technology-based roles across a variety of industries, including publishing, media and entertainment, and financial and insurance services. Our Chief Information Security Officer (“CISO”), who reports directly to the CIO, has extensive cybersecurity knowledge and skills gained from over 25 years of work experience serving in executive security roles and in a variety of industries such as telecommunications, enterprise service companies, and healthcare.
Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block]	Our CISO also receives reports on cybersecurity threats on an ongoing basis and regularly reviews risk management measures implemented by the Company to identify and mitigate cybersecurity risks.
Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag]	true

Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block]

Cybersecurity risk management, which involves resource commitments and management attention, is overseen both as a critical component of our overall risk management program and as a standalone program. We have implemented a risk-based, cross-functional approach to identifying, preventing, and mitigating cybersecurity threats and incidents, while also implementing controls and procedures that provide for the prompt escalation of certain cybersecurity incidents.

Our cybersecurity program uses a layered strategy, relying on technology and human processes to safeguard our client’s data. We embed controls within our business processes and technology development, starting with design and engineering and extending to operations. Our defense-in-depth strategy utilizes numerous layers of security controls, processes, and procedures across our information systems and networks, including but not limited to, vulnerability management, multi-factor authentication (MFA), identity access management (IAM), privileged access management (PAM), endpoint security, mobile security, application security, encryption, network security, cloud security, web security, and event monitoring and logging. Aspects of our program undergo several annual independent third-party audits and reviews, and are part of continuous bug bounty and responsible disclosure programs. We regularly review and update our cybersecurity program to address emerging threats and maintain alignment with industry best practices.

We maintain a written Information Security Policy, which establishes the foundational components of our cybersecurity program and our high-level security responsibilities over all technologies, facilities and data. When engaging service providers and third-party vendors, we perform due diligence to assess whether these providers have appropriate privacy and security controls, and we generally require these providers to implement appropriate protective measures, and to use confidential information solely for the purposes of performing their services.

Additionally, we have adopted a documented Incident Response Plan that applies in the event of a cybersecurity incident to provide a standardized framework for response. Our incident response process generally follows the NIST 800-61 framework and focuses on four phases: preparation; detection and analysis; containment, eradication and recovery; and post-incident remediation.

We have implemented a security training and awareness program for all Gartner employees and third-party contractors. Employees receive security training in connection with onboarding as well as annual awareness and training activities throughout their employment. Further, Gartner carries cybersecurity insurance covering the company and its subsidiaries.

Material Cybersecurity Risks, Threats & Incidents.

While we have not experienced any material cybersecurity threats or incidents, there can be no guarantee that we will not be the subject of future successful attacks, threats or incidents. Additional information on cybersecurity risks we face can be found in Part I, Item 1A “Risk Factors” of this Report under the heading “Strategic and Operational Risks – We are exposed to risks related to cybersecurity,” which should be read in conjunction with the foregoing information.

Cybersecurity Risk Management Processes Integrated [Text Block]

Cybersecurity risk management, which involves resource commitments and management attention, is overseen both as a critical component of our overall risk management program and as a standalone program. We have implemented a risk-based, cross-functional approach to identifying, preventing, and mitigating cybersecurity threats and incidents, while also implementing controls and procedures that provide for the prompt escalation of certain cybersecurity incidents.

Cybersecurity Risk Third Party Oversight and Identification Processes [Flag]

true

Cybersecurity Risk Board of Directors Oversight [Text Block]

The Audit Committee has the primary responsibility of assisting our Board of Directors in overseeing risks related to cybersecurity matters. The Board and the Audit Committee receive quarterly cybersecurity-related reports from our Chief Information Officer (“CIO”), that address several topics, including cybersecurity strategy, the threat environment, the status of ongoing information security program initiatives, and information security program metrics. Additionally, we have documented protocols by which certain cybersecurity incidents that meet established reporting thresholds are escalated within the Company and, where appropriate, reported to the Board and/or the Audit Committee.

At the management level, our CIO, who reports directly to the CEO, has over 20 years of experience serving in IT management, software development, and technology-based roles across a variety of industries, including publishing, media and entertainment, and financial and insurance services. Our Chief Information Security Officer (“CISO”), who reports directly to the CIO, has extensive cybersecurity knowledge and skills gained from over 25 years of work experience serving in executive security roles and in a variety of industries such as telecommunications, enterprise service companies, and healthcare. Our CISO is responsible for understanding, managing, and communicating cybersecurity risk internally to our management, and works closely with our Legal & Compliance team to oversee compliance with legal, regulatory, and contractual security requirements.

Our CISO heads the Information Security Team, which is responsible for implementing, monitoring, and maintaining cybersecurity and data protection practices across our business. The Information Security Team covers a wide range of cyber and information security responsibilities. Our CISO also receives reports on cybersecurity threats on an ongoing basis and

regularly reviews risk management measures implemented by the Company to identify and mitigate cybersecurity risks. In addition to our internal capabilities, we also engage external consultants, legal counsel, or other third-party advisors to assist with assessing, identifying, and managing cybersecurity risks.

Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block]

The Audit Committee has the primary responsibility of assisting our Board of Directors in overseeing risks related to cybersecurity matters. The Board and the Audit Committee receive quarterly cybersecurity-related reports from our Chief Information Officer (“CIO”), that address several topics, including cybersecurity strategy, the threat environment, the status of ongoing information security program initiatives, and information security program metrics. Additionally, we have documented protocols by which certain cybersecurity incidents that meet established reporting thresholds are escalated within the Company and, where appropriate, reported to the Board and/or the Audit Committee.

At the management level, our CIO, who reports directly to the CEO, has over 20 years of experience serving in IT management, software development, and technology-based roles across a variety of industries, including publishing, media and entertainment, and financial and insurance services. Our Chief Information Security Officer (“CISO”), who reports directly to the CIO, has extensive cybersecurity knowledge and skills gained from over 25 years of work experience serving in executive security roles and in a variety of industries such as telecommunications, enterprise service companies, and healthcare. Our CISO is responsible for understanding, managing, and communicating cybersecurity risk internally to our management, and works closely with our Legal & Compliance team to oversee compliance with legal, regulatory, and contractual security requirements.

Cybersecurity Risk Management Positions or Committees Responsible [Flag]

true

Cybersecurity Risk Management Expertise of Management Responsible [Text Block]

At the management level, our CIO, who reports directly to the CEO, has over 20 years of experience serving in IT management, software development, and technology-based roles across a variety of industries, including publishing, media and entertainment, and financial and insurance services. Our Chief Information Security Officer (“CISO”), who reports directly to the CIO, has extensive cybersecurity knowledge and skills gained from over 25 years of work experience serving in executive security roles and in a variety of industries such as telecommunications, enterprise service companies, and healthcare.

Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag]

true