WA political parties are using Facebook data to target voters like never before using a game-changing strategy straight out of the Donald Trump election handbook.

The data has become an integral part of campaigning for the Liberals, the ALP and the Greens — giving them an intimate insight into your private life often without you realising.

For a price, Facebook advertising allows them to know your age, occupation, interests, friendship networks and what pages you may or may not like.

It enables parties to build voter profiles to target specific demographics with different messages, and ensures dock-knocking volunteers do not waste their time on electors they have no chance of winning over.

Digital strategist from public relations firm Cannings Purple Ruth Callaghan said Facebook owned all activity data, regardless of privacy settings, making users "an absolutely saleable, marketable piece".

"Micro-targeting allows them to understand where you live, what you do, whether you own your own home, whether you are angry with political status quo, if you like triggers that indicate what political party you would normally support," she said.

"You can combine that information very easily and cheaply on Facebook and use that to push a message out to an individual voter or small group in an effective way."

In a statement, Facebook said the company does not sell individuals' information to anyone and never will.

Data provided for advertising is anonymous and not linked to a person's individual profile or identity.

"We recognise people place a lot of trust in us to protect the information they share on Facebook. We think carefully about how we can best honor the commitments we've made around privacy by giving people control over their information, being transparent about how we use that information, and being accountable to our users and regulators," a spokesperson said.

How does micro-targeting work?

After about 10 likes, Facebook can make a judgement about your gender, sexuality, or if you are conservative or left-leaning. Hundreds of likes enable Facebook to build a very detailed profile.

Liberal, Labor and Greens are all using Facebook advertising as part of their WA election strategies. ( Supplied: Cannings Purple )

"It can be that Facebook knows more about you than your parents do, your partner does, than you even do yourself," Ms Callaghan said.

When a volunteer or politician knocks on your door, they may already know what might persuade you and if they should bother spending 15 minutes talking to you.

Ms Callaghan said Mr Trump's election strategy and the Brexit campaign relied very heavily on micro-targeting.

"That information was sitting on apps for people who knocked on the front door and they knew exactly what they had to say to persuade someone to vote in a particular way," she said.

"It is a really powerful use of the big data … and it is absolutely going to change every election coming forward.

"Any party that is now isn't using it, isn't doing their job properly."

Advertising tailored to fit

Greens WA social media coordinator Madi De Jong said Facebook analytics provided crucial insights for the party's campaign.

"We can see age, gender, location, other pages people are interested in, where they share their interests from, where they are getting their news," she said.

"It's definitely informing where we are sending our message … and we can tailor our things to suit them."

State Secretary of WA Labor Patrick Gorman said getting young people to share Labor's posts was the main target for the party.

"It's about working smarter, and making sure the right people see the message that's relevant to them," he said.

Mr Gorman said the party was seeing an increase in individual donations and volunteer activity every time a post was pushed out.

A WA Liberal spokesman said the party was using Facebook to quickly distribute information like announcements to the "relevant target audience" in its largest-ever social media campaign.

Volunteers call voters from the Greens WA campaign office. ( ABC News: Laura Gartry )

'Dark posts' invisible to everyone except the target group

Previously, political campaigns have centred on newspapers advertisements, TV and radio ads and letterbox drops.

But Facebook also uses "dark posts" which can only be viewed by a target audience.

For posts to be targeted, they have to be paid for as "boosted" posts in a user's news feed, and Facebook is increasingly prioritising this in a bid to increase its revenue stream.

"You can say I would like to get a message to 18 to 25-year-olds who live in Ellenbrook who are concerned about the lack of transport. It won't appear on the website, it's going to appear only their own Facebook feeds," Ms Callaghan said.

"That makes it very hard for the outside world to judge the impact and extent of how this takes place."

But Ms Callaghan said "dark posts" could also be risky.

"When you start to choose a group based on issues such as "I don't like a particular ethnic group", you can have some dangerous racially driven micro-messaging taking place," she said.

"There are quite a lot of anti-Islamic groups that are active at the moment, their messaging is not going to be seen by the broader population."

Many of the darker posts are not coming from the major parties but from interest groups that are aligned to the parties — meaning you might be seeing a very different stream of information on Facebook from someone with differing political views.

"There are an increasing number of people who only see what Facebook presents to them and Facebook is under no obligation to give you a balanced position," Ms Callaghan said.

Combined with the electoral roll Facebook data can inform door knocking. ( Supplied: WA Labor )

Call centres increasingly irrelevant

In 2016, 15 million Australians were on Facebook, with the average Australian user logging on to the site 32 times a week.

About a third of all users, and half of those aged 30-39, say they get their news from social media, and at the same time many people are disconnecting their land lines, or simply do not answer unknown numbers.

As a result, Ms Callaghan believes voter phone call centres are becoming increasingly irrelevant.

"What is much more effective is if you can get an SMS out to the public. We saw that in the federal election with Labor's use of the Medicare campaign. It is effective, it feels personalised and it comes straight to the person," she said.

The WA Greens are training their volunteers to have persuasive online conversations.

Campaign manager Andrew Beaton said it was the same principle as door knocking without the constraints of distance.

"It can be as simple as we provide a banner image or profile image and that can engage people in conversation, or if they want they can talk to people on their wall, and talk to people in community groups online," he said.

"It also gives people the opportunity to check in with us if they need help."

Mr Beaton said door knocking and phone calls would remain an important part of the party's strategy, but social media was equally vital in the future.