PhD defense: Everything you need to know

A PhD defense, also known as a PhD viva, is an oral examination in which a doctoral candidate presents and defends their dissertation before a panel of academic examiners. The examiners assess the originality, rigour and contribution of the research and question the candidate to evaluate their understanding and critical engagement with the topic. The outcome determines whether the candidate is awarded the doctoral degree, which is often subject to revisions.

This blog post outlines what a PhD defense entails, including its purpose, format, possible outcomes and common questions. Moreover, it explains who attends, how long the defense typically lasts and when professional editing can support thesis preparation. It also offers practical tips, resources and statistics to help PhD candidates navigate the viva process with confidence.

Key takeaways

PhD defense’ and ‘PhD viva’ are interchangeable terms depending on country and context
The defense tests research quality, originality and the candidate’s ability to explain and defend their work
Most vivas involve internal and external examiners and may be public in countries like Sweden and the Netherlands
The defense usually lasts 1.5–3 hours and ends with an outcome ranging from pass to fail, with most candidates required to make revisions
Professional editing services can improve clarity, style and formatting of the PhD thesis/dissertation before and after the defense
Common viva questions focus on research motivation, methodology, findings, and critical reflection
Appeals are possible but usually limited to procedural issues — not academic judgement
UK pass rates are high (96%), with most candidates asked to make minor or major corrections
Preparation should include practising answers, reviewing the thesis, anticipating questions and understanding examiner perspectives

Other names

While ‘PhD defense’ is a common term, especially in the USA, different countries and institutions use various names for the final doctoral examination. Although the terminology differs, all these terms refer to the same core process: an oral exam in which the candidate defends their doctoral research before a panel of academic examiners.

Other names include:

PhD viva: Short for viva voce, Latin for ‘with the living voice,’ this is the preferred term in the UK, Ireland and some Commonwealth countries.
Doctoral examination: A generic term used in formal university documentation.
Disputation: Used in parts of Europe, such as Sweden and Finland, to describe a public academic debate based on the dissertation.

Purpose

The purpose of a PhD defense is to evaluate whether the candidate has conducted original, rigorous research and can clearly explain and justify their findings. It serves as a formal examination that determines if the candidate meets the standards required to be awarded a doctorate.

Here are the key goals of a PhD viva:

Demonstrate expertise: PhD candidates must show deep knowledge of their research area, including relevant theories, methods and existing scholarship.
Defend your argument: PhD candidates need to clearly explain their thesis, justify their research decisions and respond to critical questions from the examiners.
Show independence: The defense tests whether the PhD candidate can think critically, make sound academic judgments and contribute new insights to their field.
Confirm originality: Examiners check that the work is original, properly cited and represents a meaningful contribution to academic knowledge.
Improve: In many systems, the PhD viva also gives the PhD candidate a final opportunity to clarify, revise or improve their dissertation before final submission.

Format

The format of a PhD defense typically follows 3 main stages: preparation before the defense, the event on the day, and post-defense outcomes. While practices vary slightly by country and institution, the core structure remains consistent.

Before the PhD defense

Submission of the dissertation: The PhD candidate submits their final draft of the dissertation/thesis to the graduate school and examiners within a required timeframe.
Appointment of examiners: The university appoints internal and external examiners to evaluate the dissertation and attend the PhD viva.
Pre-viva review: Examiners read the dissertation and prepare questions and comments.

On the day of the PhD defense

Presentation (if applicable): Some universities begin with a presentation (usually 10–20 minutes) where the candidate summarises their research. Others proceed directly to questioning.
Oral examination: The core of the PhD defense involves detailed questioning from the examiners. This can last 1–3 hours, depending on the institution.
Deliberation: After questioning, the candidate leaves the room while the examiners discuss the outcome.
Initial outcome: The chair or lead examiner announces the result, which may include minor or major revisions, a pass, or (rarely) a fail.

After the PhD defense

Revisions (if required): Most candidates are asked to submit corrections within a set timeframe, ranging from 2 weeks to 6 months.
Final approval: Once revisions are accepted, the university formally approves the doctorate.
Graduation: The student receives their degree at a graduation ceremony or via official documentation.

Preparing PhD dissertation for the defense

PhD candidates can use professional editing services to improve language, consistency and formatting of their thesis/dissertation at 2 key stages: before the PhD defense and after making post-viva revisions. Choosing the right service — copyediting or proofreading — ensures that the dissertation meets institutional standards and communicates its findings clearly.

Before the defense

Submit a polished draft to examiners: The candidate should hire a copyeditor before submitting the thesis for the PhD defense. The copyeditor improves grammar, corrects awkward phrasing, enforces style consistency and ensures clear structure.
Respond to supervisor feedback on writing quality: When supervisors highlight unclear language or inconsistent presentation, the candidate benefits from professional copyediting to improve readability and correct stylistic issues.
Address language challenges when using English as a second language: A copyeditor helps candidates using English as a second language remove ambiguity, clarify complex ideas and align the writing with academic norms, reducing potential misunderstandings during the viva.
Ensure compliance with university formatting guidelines: A proofreader can help ensure table and figure captions, page numbers, reference styles and layout match institutional requirements before the thesis reaches the examiners.

After the defense

Revise the thesis after receiving examiner feedback: After the viva, the candidate may need to rewrite sections based on examiner comments. A copyeditor ensures that revised content integrates smoothly with the rest of the text and maintains a consistent tone.
Finalise the document for university submission: Before submitting the final version, the candidate should use a proofreader to catch typographical errors, inconsistencies and minor formatting issues that remain after revisions.
Prepare chapters for publication: When converting dissertation chapters into journal articles or a book, the candidate can work with a copyeditor to reframe the material for new audiences and adapt it to the relevant style guide.

Attendees

The attendees of a PhD defense vary by country and institution, but they typically include the following:

PhD candidate: The candidate presents and defends their dissertation. They respond to questions and justify their research decisions.
Examiners: Most defences include 2 or more academic examiners:
1. Internal examiner: A faculty member from the candidate’s institution who is not involved in supervising the thesis.
1. External examiner: An expert from another university or research body who provides an independent evaluation.
1. Some institutions appoint additional examiners or subject specialists.
Chairperson or moderator: Some universities appoint a neutral chair to ensure the defense runs according to regulations and that examiners follow protocol.
Supervisor(s): In some systems (e.g. the UK), supervisors may attend as silent observers but cannot speak or intervene. In others (e.g. parts of Europe), supervisors may participate in the questioning.
Audience (optional): In many European countries, such as Norway, Sweden, the Netherlands, Austria, and Belgium, PhD vivas are public events. Academic staff, students or guests may attend and, in some cases, ask questions during a designated period. In the UK and US, the viva is usually closed, with only authorised individuals present.

Duration

The duration of a PhD defense varies depending on the institution, subject area and examination format. Ultimately, the duration depends on how thoroughly the examiners explore the thesis and how long the candidate takes to respond. However, most defenses follow this general range:

Typical length: Most PhD vivas last between 1.5 and 3 hours. This includes an initial presentation (if required) and a structured question-and-answer session.
Shorter defenses: In some fields, particularly in the humanities or social sciences, the viva may take 60–90 minutes if the dissertation is concise and the examiners have few major concerns.
Longer defenses: In technical or experimental disciplines, the viva may extend up to 4 hours, especially if the work is complex or involves detailed data analysis.
Public vs closed formats
- In countries like the Netherlands or Sweden, public vivas may include ceremonial elements and take 2–4 hours, sometimes with additional formalities.
- In the UK or US, the PhD viva is typically closed and more focused, lasting 1.5–2.5 hours on average.

Outcomes

The outcome of a PhD viva depends on the candidate’s performance during the oral examination and the quality of their dissertation. Most universities use a set of standard categories to classify the result. These may vary slightly by institution, but the core outcomes typically include:

Pass with no corrections: The candidate receives immediate approval with no changes required. This is rare and reflects an exceptional dissertation and defense.
Pass with minor corrections: The candidate needs to make small changes such as clarifying arguments, correcting typos or improving formatting. They usually have a few weeks to complete these.
Pass with major corrections: The candidate must revise key sections of the dissertation, such as methodology, analysis or structure. This may take several months and often requires examiner approval after resubmission.
Resubmission required: The candidate needs to rewrite significant parts of the dissertation and submit it again for full re-evaluation. A second PhD viva may be required. This outcome signals that the work shows promise but is not yet of doctoral standard.
Fail with option to award a lower degree: In some cases, examiners recommend awarding a Master’s degree (e.g. MPhil) instead of a doctorate if the work meets that level. For instance, the University of Leeds specifies that for candidates submitting for a PhD only, examiners may recommend the award of an MPhil (with or without minor corrections) if the thesis fails to achieve the standard for a PhD but satisfies the criteria for an MPhil.
Fail with no award: This is rare and occurs when the dissertation is fundamentally flawed and not suitable for resubmission. Most institutions treat this as a last resort.

Each outcome reflects a judgment about the originality, rigour and clarity of your work. Most candidates pass their PhD defense, often with minor or major revisions.

Pass rates

PhD defense pass rates are consistently high, especially in systems where candidates undergo rigorous review before reaching the viva stage. Below are the most recent statistics from reputable sources in the UK and US, with each statistic followed by its source in brackets.

United Kingdom

According to this 2006–2017 study study of 26,076 candidates at 14 UK universities:

96% of candidates pass their PhD viva
79% of passing candidates are required to make minor corrections
16% are asked to undertake major corrections
3.3% fail their viva examination
80.5% of all enrolled PhD students complete their doctorate

United States

56.6% of doctoral students complete their degree within 10 years (Council of Graduate Schools, 2008 cohort baseline report)
Up to 40–50% of PhD students in the US do not complete their programmes (Springer, 2017 analysis of doctoral attrition)
Princeton University reports a PhD completion rate of 80% within 10 years for most departments (Princeton Graduate School cohort analysis)
Doctoral degree conferrals in the US rebounded to an all-time high in 2022–2023 (Forbes, citing NCES data)

Appeal

Most universities allow appealing the outcome of a PhD defense, but only under specific circumstances. Appeals must follow institutional procedures and are usually limited to procedural or fairness issues rather than academic judgement.

Grounds for appeal typically include:

Procedural irregularities: For example, if the examination did not follow university regulations or there were administrative errors.
Bias or misconduct: If one or more examiners behaved inappropriately, showed bias or had a conflict of interest.
New evidence: If relevant information emerged that could not have been submitted earlier and may have affected the outcome.

What cannot be appealed:

The candidate cannot challenge the academic judgement of the examiners simply because they disagree with their decision or feedback.

Appeal process

The candidate must submit a formal appeal within a defined timeframe, usually 10–30 working days after receiving the decision.
The university reviews the case, often through an academic appeals board or equivalent panel.
If the appeal is upheld, possible outcomes include a re-examination, appointment of new examiners or withdrawal of the original decision.

Common PhD defense questions

During a PhD viva, examiners test the candidate’s understanding of their research, ability to justify their choices and their awareness of the broader academic context. While questions vary by field, many follow recurring themes.

Thesis motivation and scope
- What motivated you to pursue this topic?
- What is the main research question?
- Why did you choose this particular theoretical framework?
Methodology
- Why did you choose this method?
- What are the limitations of your approach?
- How did you ensure reliability and validity?
Literature and context
- How does your work relate to existing literature?
- What are the key debates in your field, and where do you position your research?
- Are there any significant works you excluded, and why?
Findings and analysis
- Can you explain your key findings?
- Were there any unexpected results?
- How do your findings advance knowledge in your area?
- What is the significance of your findings?
Critical reflection
- What are the strengths and weaknesses of your research?
- If you were starting again, what would you do differently?
- How do you respond to critiques of your work?
Contribution and future research
- What is the original contribution of your thesis?
- How can your research be applied in practice or policy?
- What are the next steps in this line of research?

Preparation tips

To prepare for a PhD defense, review the dissertation thoroughly, anticipate questions, rehearse responses, and research the examiners’ backgrounds to align with their academic perspectives.

Know your thesis inside out: Review your dissertation thoroughly. Understand your arguments, data, methods and any areas your supervisors flagged as potentially weak.
Rehearse your answers: Practise explaining your research clearly. Ask peers or mentors to conduct a mock viva using common PhD defense questions.
Prepare a concise presentation: If required, create a summary presentation (10–20 minutes) that highlights your main findings and contribution. Practise for clarity and timing.
Anticipate examiner questions: Prepare for both general and specific questions. Think about how your findings relate to broader debates and possible critiques of your approach.
Research your examiners: Read your examiners’ recent publications and identify their research interests. This helps you anticipate the types of questions they may ask and the perspectives they may bring.
Understand your contribution: Be ready to articulate your original contribution and how your work fills a gap, challenges assumptions or opens new directions in your field.
Reflect on limitations: Be honest about the limitations of your study. Explain how you addressed them and how they might inform future research.
Clarify technical aspects: If your work includes complex methods or theory, prepare clear explanations. Use examples where necessary to make your points accessible.
Know the process: Familiarise yourself with the viva structure, including who will attend, how long it will last and the possible outcomes.
Rest and stay composed: Get adequate rest before the viva. Arrive early, dress professionally and treat the defense as an academic discussion.

Resources

How to Survive Your Viva: Defending a Thesis in an Oral Examination by Rowena Murray offers structured guidance on anticipating questions and developing confident responses.
The UK’s Vitae programme also offers relevant guides.
The Thesis Whisperer offers blog posts and practical advice on the viva and academic writing.
FindAPhD provides articles on viva preparation and PhD life.
Peer support and mock vivas: Organise mock vivas with peers or supervisors to simulate real conditions. You can also join online forums such as The GradCafe for shared experiences and advice.

Conclusion

The PhD defense is a key academic milestone that validates the candidate’s research and scholarly competence. With careful preparation, awareness of institutional norms and attention to feedback, most candidates succeed — often after completing revisions. Understanding what to expect at each stage can significantly reduce stress and improve performance.

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