The deal will update the 18-year-old IT Agreement and add 200 products to the zero tariff list.
It is expected to give a boost to producers of goods ranging from video games to medical equipment.
The WTO says the sum is equal to global trade in iron, steel, textiles and clothing combined.
"Today's agreement is a landmark," said WTO Director-General Roberto Azevedo.
"Eliminating tariffs on trade of this magnitude will have a huge impact," he continued.
"It will support lower prices - including in many other sectors that use IT products as inputs - it will create jobs and it will help to boost GDP growth around the world."
The final technical details will be worked out until December.
The existing 1996 IT agreement was seen by industry and policy makers as woefully out of date as it did not cover devices and products invented since then.
Products added range from advanced computer chips to GPS devices, medical equipment, printer cartridges and video-game consoles
Technology manufacturers such as General Electric, Intel, Texas Instruments, Microsoft and Nintendo are among the many companies expected to benefit from the deal.
Negotiations on updating the technology agreement began in 2012.
Analysis: Andrew Walker, BBC World Service economics correspondent
Finally, the WTO has brought its Information Technology Agreement (ITA) into the 21st century.
This was the first tariff cutting agreement the WTO has managed since ITA 1.0, as it is not officially known, was agreed.
The key political deal was done in 1996 at a WTO ministerial conference in Singapore. Sadly, you might think, I was there and am still covering the same story, though I have had very little reason to think about this one since.
Still this is an important step, and it is the second one the WTO has taken in two years - a very short period in the geological timescales of trade negotiations.
The other was an agreement on simplifying trade procedures, the one concrete achievement of the negotiations called the Doha Round launched in 2001.
So a significant step towards more liberalised trade has been taken. But the WTO has the rest of the wide ranging and complex Doha Round still to do.
The World Trade Organisation (WTO) has struck a "landmark" deal to cut tariffs on $1.3 trn (£838bn) worth of technology products.