The PhD Viva: What Exactly Happens and How to Prepare
What a viva voce is, who's in the room, and the possible outcomes
The 30-second summary
A viva (short for viva voce) is the oral exam at the end of a UK PhD, where usually two examiners question you about your thesis behind closed doors.
- It’s a conversation, not a presentation. Most last two to four hours and work through the thesis chapter by chapter.
- Corrections are the normal result. Passing with no changes at all is rare; minor or major corrections are common.
- Preparation is mostly rehearsal. Re-read your thesis, summarize it in five minutes, and sit a mock viva if you can.
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The viva is the last exam of your PhD, and it’s the one nobody can fully describe in advance. It happens behind a closed door, every university runs it slightly differently, and the stories that reach you tend to be the dramatic ones. That leaves a lot of room for dread.
Having coached students through their degrees for the last 10 years, we’ve found that most of that dread comes from not knowing what to expect. In this post, we’ll explain what happens in a viva, who will be in the room and what the possible outcomes are, and then share how to prepare.
What is a viva?
A viva voce, or viva for short, is an oral examination of your thesis. The Latin means “by living voice”, and that’s the point of it: your examiners have already read the thesis, and the viva is where you talk them through it. It’s the standard final step of a PhD in the UK, and it’s used for some master’s degrees too.
The University of Edinburgh’s guide puts its purpose plainly. In the viva, you’ll be “convincing the examiner that the work is original, that it is your own work, and that it makes a contribution to knowledge that it is worthy of the award of PhD.”
With AI tools and ghostwriting services able to produce what looks like fluent academic writing, a live conversation about your own choices is one of the clearest ways to show the work is yours, which makes the viva matter more than ever.
Viva vs dissertation defense
If you’ve read American advice about the “dissertation defense”, be careful, because the two exams differ in ways that change how you prepare. In the US, a defense is often a public event that opens with your presentation. Portland State University, for example, states that “dissertation defenses are open to the public” and expects the candidate “to prepare and give an oral presentation on the research methodology and results”.
Here’s how the two compare:
| UK viva | US defense | |
|---|---|---|
| Who attends | You and your examiners, in a closed room | Your committee, and often an audience |
| Format | A discussion of the thesis | Often a presentation, then questions |
| Examiners | Usually one internal and one external | A committee of several faculty members |
Both terms are used loosely, though, and some UK universities ask for a short presentation at the start of the viva. Check your own university’s regulations rather than relying on either label. For the US version, our guide to preparing for a dissertation defense covers the questions committees tend to ask.
Who’s in the room
In the UK, you’ll normally face two examiners. The internal examiner is an academic from your own university, and the external examiner is an expert in your field from another institution. The external brings an outside view, judging your thesis against the standard of your field as a whole.
Some universities appoint a second external examiner instead of an internal one, for example if you’ve worked at the university, and some have an independent chair run the viva without examining you. Lancaster’s examination guidance sets out both.
Some universities also appoint an independent chair, who doesn’t examine you but makes sure the viva follows the rules and is run fairly. Whether your supervisor (your advisor, in US terms) can attend varies. At Loughborough, for example, one member of your supervisory team may sit in as an observer, “but only where the doctoral researcher has indicated that they wish them to be present.”
What happens on the day
Most vivas run for a few hours. The University of St Andrews says they “usually last between two to four hours”, and Edinburgh adds that a long one is not a bad sign: the length “reflects the amount of time taken to go through the thesis and how in-depth the examiners want to take the discussion.”
Most vivas follow the same shape. The examiners start with a broad question, something like “Could you summarize your thesis in a few minutes?” Then they work through the thesis, often chapter by chapter, asking why you made the choices you did and what your findings add to the field. Most universities let you bring your own copy of the thesis. Loughborough’s code of practice says candidates “should be allowed to consult a copy of their thesis (which may be annotated in physical or electronic form)”.
When the discussion ends, you’ll normally be asked to step out while the examiners agree on a result. Then they invite you back in and tell you, usually on the same day.
The possible outcomes
This is the part that worries most students, so it’s worth knowing the options before you walk in. Read the figure below for two things: how few of the outcomes mean failure, and how many end with a PhD after some revision.
Here’s what each outcome means in practice, using the University of Sheffield’s regulations:
| Outcome | What it means | Time allowed (Sheffield) |
|---|---|---|
| No corrections | The degree is awarded as the thesis stands | None needed |
| Minor corrections | Small fixes to the thesis | 3 months |
| Major corrections | Substantial revisions, but no second viva | 6 months |
| Resubmission | A revised thesis, which may be examined again | 1 year |
| MPhil instead | A master’s degree is awarded instead of the PhD | None, or 1 year to revise for it |
| Fail | The degree is not awarded | None |
Timings and names vary between universities. Leeds, for example, moved its minor-amendments deadline from twelve weeks to six months in September 2026. So treat the table as typical and read your own university’s list before the day.
The most useful thing to take from it is that corrections are the normal result. Edinburgh’s guide describes a pass with no corrections as something that “happens very rarely”, while minor and major corrections are both “common”. If your examiners ask for corrections, that’s the usual way to pass.
How to prepare for your viva
Vivas vary a lot from one to the next. A 2023 systematic review of eight studies, covering 267 candidates, found “a great deal of variation” in how candidates experienced them, from constructive to distressing. You can’t choose your examiners, but you can control how prepared you are, and preparing is less about learning anything new than being ready to talk about what you’ve already done. Here are the five things we’d focus on.
1. Re-read your thesis and annotate it
Read the whole thesis again in the weeks before, as if you were the external examiner. Mark the key arguments, the places you made a judgment call, and any errors you spot (examiners find typos too, and pointing one out first shows you know your work). Small tabs on each chapter make it easy to find things under pressure.
2. Prepare a five-minute summary
Expect to be asked to summarize your thesis at the start, and practice the answer out loud until it’s natural. It should cover your research question, why it matters, how you answered it and what you found. A good opening answer sets the tone for everything after it.
3. Know your limitations before they do
Your examiners will probe the weaknesses in your study, so get there first. List the main limitations of your design, sample and analysis, and prepare a calm answer for each: why you made that choice, what it costs and why your findings still hold. For example:
Notice how the answer names the trade-off, gives the evidence and then concedes the limit, without getting defensive. Our guide to research limitations shows how to frame them in the thesis itself.
We work through nine questions examiners often ask in this walkthrough, with an example answer for each. Watch how the strong answers explain why a choice was made, not just what it was.
4. Sit a mock viva
A mock viva is a practice run with someone playing the examiner, ideally your supervisor or an experienced colleague. It’s the closest thing to the real exam, and candidates who have done one rate it highly. In Davis and Engward’s 2018 study of eighteen candidates, all thirteen who had sat a mock viva “were supportive of the value of this approach in helping them to prepare their arguments and to consider possible questions from the examiners.”
5. Read your examiners’ work
Your external examiner was chosen because their research is close to yours, so read their recent papers. You’ll get a sense of the angles they may take, and you can make sure you’ve engaged with their work where it’s relevant. Also check what’s been published in your field since you submitted, since examiners often ask about it.
None of this guarantees an easy viva, but it changes what you walk in with. You’ll know the format, you’ll have said your summary out loud, and you’ll have heard the hard questions before. That leaves you free to do what the viva is actually for: talking about your research with people who have read every page of it.
Want to rehearse with someone who has sat on the other side of the table? Our doctoral-qualified coaches run mock vivas over video. They’ll question you as an examiner would, then go through your answers so you know what to tighten.
Still have questions?
Can you fail a PhD viva?
Yes, but it isn’t one of the usual results. Edinburgh’s viva guide lists the four most common outcomes (no corrections, minor corrections, major corrections and resubmission), and an outright fail isn’t among them. A thesis that isn’t ready yet is far more likely to be sent back for revision.
How long does a PhD viva last?
Usually two to four hours, though some are shorter and a few run longer. The length mostly reflects how deeply the examiners want to discuss the thesis, so a long viva isn’t a sign that it’s going badly.
Can my supervisor attend my viva?
It depends on your university. Some let one supervisor sit in as an observer if you ask for them, while others are stricter. Check your university’s code of practice, and decide early whether you want them there.
Is a viva the same as a dissertation defense?
They’re both oral exams of a thesis, but the formats differ. A UK viva is a closed discussion with two examiners, while a US defense is often public and opens with a presentation to a committee. Always check what your own university expects.
Do master’s students have a viva?
Some do, particularly research master’s degrees such as the MPhil. Your program handbook will say whether yours includes an oral exam.
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