What Is a PhD Viva? Format, Examiners, Outcomes and Preparation

A PhD viva, short for viva voce, is an oral examination held after you submit your doctoral thesis. It gives you the opportunity to defend and clarify the thesis while examiners test your knowledge of the field, the originality and quality of the research, your decisions, and whether the work is genuinely yours.

The thesis and the viva work together as the final doctoral assessment. The UK Quality Assurance Agency describes final doctoral assessment as a thorough review of the submitted work followed by an oral examination at which the candidate defends the thesis. Your own university's regulations remain decisive because examiner arrangements, format, duration, attendance and outcome categories vary.

The PhD viva process at a glance

This sequence reduces uncertainty, but it is not a universal timetable. For example, some institutions permit remote vivas, some may require a short presentation, some allow a supervisor to attend without participating, and some use an independent chair. Confirm each operational detail with your doctoral school or research degree office.

1. What is the purpose of a PhD viva?

Cambridge identifies four functions: allowing the candidate to defend and clarify the thesis, probing knowledge of the field, confirming that the work is the candidate's own, and enabling examiners to reach an examination outcome. UCL similarly instructs examiners to determine whether the thesis meets the criteria for the degree and whether its requirements have been satisfied.

These functions explain why viva questions often go beyond asking what you did. Examiners may ask why you chose a method, what an alternative would have changed, where your strongest evidence sits, which claim is genuinely original, or how a limitation restricts the conclusion.

2. Who examines you?

The QAA states that a minimum of two examiners are usually present in UK doctoral oral examinations, commonly one internal examiner and at least one external examiner. The internal examiner understands the institution and normally works within it. The external examiner contributes independent subject expertise from outside the institution.

An independent chair or convenor may also attend to support procedural fairness. Supervisor attendance is governed by local rules. For example, Cambridge states that a supervisor cannot attend its viva, while UCL says a supervisor may be invited but does not have the right to participate. This is why generic advice should never override your own examination regulations.

3. What happens during a PhD viva?

The examiners should explain the procedure at the beginning. The discussion may then move through the thesis in chapter order or follow themes such as contribution, literature, methodology, findings and limitations. UCL notes that there is no single formal procedure and that very few examiners conduct a page-by-page criticism.

You may be asked for a short thesis overview. You may also be asked to locate a table, explain a disputed interpretation, compare alternative methods, clarify collaborative work, or state what you would change. The objective is not to deliver a memorised lecture. It is to answer the question asked and make the reasoning visible.

4. How long does a PhD viva last?

There is no universal duration. Cambridge says there is no set length but that a viva normally lasts between 90 minutes and three hours. UCL states that there is no formal limit and that its vivas typically last around two to three hours. Discipline, thesis format, institutional practice and the issues identified by examiners can all affect length.

Duration is not a reliable result signal. A short viva does not prove that the outcome is positive, and a long viva does not prove that it is negative. Prepare for sustained discussion, ask about breaks and accessibility arrangements in advance, and do not interpret the clock while you are being examined.

5. What do examiners assess?

The exact criteria come from your institution and degree regulations. Across UK guidance, recurring assessment areas include originality, contribution to knowledge, command of the field, research ownership, methodological judgement, quality of evidence, critical analysis, and the defensible scope of conclusions.

• Contribution: What does the thesis add, and at what level?
• Ownership: Which decisions and work are yours, especially in collaborative research?
• Methods: Why did the design fit the question, and what trade-offs followed?
• Evidence: Which findings support each main claim?
• Field knowledge: How does the thesis relate to relevant literature and debate?
• Limitations: What can the research establish, suggest and not establish?
• Judgement: Can you respond to criticism without exaggerating or abandoning a justified claim?

6. What questions might you be asked?

No question list can predict your viva because the examiners have read your thesis. However, most questions test a small set of underlying jobs: explain the research, defend a decision, locate evidence, bound a claim, respond to an alternative, or show what you learned.

• What is the central argument of your thesis?
• What is the most important original contribution?
• Why did you choose this methodology?
• Which alternative explanation is strongest?
• How do your findings change the existing literature?
• What is the main limitation of the study?
• Which claim would you revise if you rewrote the thesis?
• What work should follow from this research?

Use the MockBase guide to common PhD viva questions for a larger question bank and answer strategies.

7. What are the possible outcomes?

Outcome labels and consequences differ between institutions, so do not rely on a generic list as if it were your regulation. Common categories include approval without corrections, approval subject to minor or major corrections, revision and resubmission, a different degree recommendation, or failure. Some routes may require another oral examination and others may be checked by one or both examiners.

Cambridge, for example, distinguishes approval without correction, conditional approval with corrections, and several revision and resubmission routes. UCL publishes its own outcome and next-step rules. Your formal outcome letter should specify the authoritative category, required work, deadline and checking process.

8. Is a UK viva the same as a thesis defence?

The terms overlap but institutional formats differ. In the UK, viva usually refers to the oral examination of a submitted doctoral thesis. Other countries may use thesis defence or dissertation defence, and the event may include a public presentation, a larger committee or different decision procedures.

Do not transfer assumptions from another country's defence videos to your own viva. For example, whether slides are required, whether an audience attends, whether the supervisor is present and when the outcome is communicated are all local questions.

9. How should you prepare?

Start by borrowing the system already available to you. Read the official doctoral regulations and department guidance, ask your supervisor or doctoral school what normally happens, request any permitted reasonable adjustments, attend university preparation training, and arrange a mock viva with someone who can challenge the thesis.

1. Confirm the format, participants, location or online platform, presentation requirement, permitted materials and adjustment process.
2. Re-read the thesis actively and mark contribution claims, methods, key findings, limitations and possible corrections.
3. Create a one-page map linking the research question, method, evidence, findings and contribution.
4. Prepare a two-minute thesis overview without memorising a full script.
5. Practise answering aloud and invite follow-up questions on weak or ambiguous claims.
6. Prepare a calm decision rule: clarify the question, state the claim, explain the evidence, name the limitation and stop.

For a complete preparation sequence, read how to prepare for a PhD viva. To test the answers under realistic challenge, use the mock PhD viva structure and feedback checklist.

10. Frequently asked questions

What is a PhD viva?

It is an oral examination held after thesis submission. Examiners use the thesis and discussion to test research ownership, knowledge, judgement and whether the work meets the institution's doctoral award criteria.

Who examines a PhD viva?

UK vivas usually involve at least two examiners, commonly one internal and at least one external examiner. Some institutions also use an independent chair and have different rules about supervisor attendance.

How long does a PhD viva last?

There is no universal duration. Cambridge states that its vivas normally last between 90 minutes and three hours, while UCL says they typically last around two to three hours. Check your own university and department guidance.

Do corrections mean that I failed?

No. Corrections or amendments are formal routes for bringing the thesis to the required standard. The categories, deadlines, checking process and possibility of another oral examination vary, so use your formal outcome letter and regulations.