Skip to main content
Woodland Trust home page
Become a member

Grass snake or adder? How to tell the difference between UK reptiles

Rory Morrow

Digital content editor

The UK has three native species of snake and three native species of lizard. Learn where these reptiles can be found, how to spot them and how to tell them apart with our quick and easy ID guide.

Native UK snakes

Credit: pronature / Alamy Stock Photo

Adder (Vipera berus)

The Adder is clearly distinguished by a dark zigzagging line down its back, set against a grey (male) or light brown (female) body. It also has a ‘V’ or ‘X’ shaped marking on the head. Unlike the other snakes on this list, adders have vertical, slit-shaped pupils instead of round ones. Adults reach 60–80cm in length.

Adders are venomous, but bites from these shy reptiles are rare and seldom fatal. No other snake species in the UK is venomous, so it’s worth being able to recognise them! Adders are secretive and well camouflaged, so are unlikely to be stumbled upon often.

They live in open habitats where they can bask in the sun, such as heathland, moorland and open woodland.

Credit: Louise Murray / Alamy Stock Photo

Grass snake (Natrix helvetica)

Grass snakes do not have the dark zigzag pattern down their backs or the narrow, vertical pupils like adders, making them easy to tell apart. Grass snakes are grey-green coloured with black bars down their sides and a yellow and black ‘collar’ around the neck. Reaching up to 1.5m long, grass snakes are the largest reptiles in the UK.

These snakes are found throughout England and Wales, but not Scotland or Northern Ireland. They live close to water as they feed on amphibians and fish, so you might find them near garden ponds. Don’t worry though – grass snakes aren't venomous and are very shy. If cornered, they tend to play dead!

Credit: Peter Holmes / WTML

Smooth snake (Coronella austriaca)

Smooth snakes are extremely rare, found only in heathlands in Dorset, Hampshire, Surrey, Devon and West Sussex. They hide under stones and logs rather than basking in the open and are smaller than the UK's other snake species, measuring 50–70cm.

If you are fortunate enough to see a smooth snake, they are grey-brown, with two rows of black markings down their back and a heart-shaped crown on the head. They are browner than grass snakes and the black markings are on their back rather than their sides.

Smooth snakes are strictly protected by European law and reintroduction programmes are trying to save this species from extinction in Britain.

Native UK lizards

Credit: Susan & Allan Parker / Alamy Stock Photo

Common lizard (Zootoca vivipara)

Common lizards are brown (but can also be yellow, green and black) with dark spots or stripes running lengthways down the body. They are typically 15cm in length from nose to tail. Males have bright yellow or orange-speckled bellies, while females have paler, plain undersides.

As the name suggests, common lizards are widespread throughout the UK, living in commons, heaths, moorland, dry stone walls and sea cliffs.

Credit: iStock.com / Trebor Eckscher

Sand lizard (Lacerta agilis)

The male sand lizard is brown with vibrant green sides, which help to distinguish it from the common lizard. The green colours are at their brightest during the breeding season. Female sand lizards are duller, with sandy-brown bodies and dark blotches down the back. The species is larger than the common lizard, reaching 20cm in length.

The sand lizard is mainly restricted to southern England, with a few isolated populations in Wales and Merseyside, as it requires heathland and dune habitats in close proximity. Reintroductions of this species have been carried out in the South West, South East, Lancashire and Wales, to extend its range and increase the UK population.

Credit: Ian Thraves / Alamy Stock Photo

Slow worm (Anguis fragilis)

Slow worms might look like snakes, but they are actually legless lizards. To identify them, look for the eyelids and ear holes – two features which lizards have but snakes do not. Male slow worms are grey or brown, sometimes with bright blue spots, while females are golden brown, often with a thick dark line down their backs. They generally reach 40–50cm long.

Slow worms hide under logs or compost heaps, rather than basking in the sun, and may be found in gardens. They are widespread in the UK, only absent from Northern Ireland and the Scottish islands.

Did you know?

All UK reptiles are protected by national law, which makes it illegal to deliberately kill, injure or sell individuals of any species. They are fantastic to spot, but please observe them from a distance and do not disturb them.

When and where to see reptiles in the UK

The UK's snakes and lizards are most active between early spring and late autumn. This is because reptiles can't produce their own heat, so rely on warm weather instead.

When things get cold over the winter, you're less likely to see these fascinating animals as they spend most of their time tucked away in burrows or cosy leaf piles, emerging occasionally to feed during milder spells. This behaviour, known as brumation, differs from hibernation as it doesn't involve total inactivity.

Look for reptiles on warm days in sheltered areas, particularly in habitats such as heathland or grassland. You'll often find them basking on a sunny rock or patch of soil, or sheltering under warm logs, bits of corrugated metal or in compost heaps.

This blog was originally published on 1 February 2018, and was last updated on 27 August 2026 to include new information.

Boost your wildlife ID skills

Look at our full range of nature swatch books for help identifying trees, minibeasts, birds and more.

Shop now

Discover more UK wildlife