Foldable-screen phones have moved beyond a gimmick and are now clocking serious sales, says IDC.

The market research firm says sales shipments of foldables jumped from 1.9 million in 2020 to an estimated 7.1 million in 2021 - and will grow to 27.6m in three years' time, growth that would see the segment worth US$29 billion.

"The growth in 2021 can largely be attributed to Samsung's recent success, as the Korean giant made waves in the market thanks to its newest foldable flagships," IDC says.

Total sales remain modest. If shipments do hit 27.5m, that will still be under 2 per cent of the market.

* Forecast projections

But despite their small market share, foldables represent a "major opportunity" for Samsung and its rivals, IDC says - because the segment is tipped to continue growing much faster than the market as a whole, and with premium pricing to boot.

"From the consumer point of view, foldables represent the most innovative visual change to happen to smartphones and therefore it is a segment that cannot be ignored by vendors," IDC says.

"The commercial segment has also seen foldables being marketed as a replacement for both a phone and a tablet."

Samsung's Galaxy Flip4 holds appeal if you miss the flip phones of old, or are a new-school social media type after a quick-fire way to rest your phone for a stable shot. Photo / Supplied

Samsung's third-generation foldables featured in IDC's 2021 figures.

The tech giant has released the fourth-generation of its foldable range: Samsung Galaxy Z Flip4 (from $1699 - $2049) and Galaxy Z Fold4 (from $2849), with orders now open now via Spark, Vodafone and 2degrees (all offer a mix of discounts and monthly payment options if you sign up for a 12, 24 or 36-month plan).

Samsung mobile-business head Roh Tae-moon said the foldables are drawing in three times more brand switchers than Samsung's conventional Galaxy S flagship handsets.

Newcomers represented a double-digit percentage of Samsung's foldable shipments last year, he said.

He expected the fourth-generation models to draw more new buyers to the brand.

"We consider this to be a quite meaningful percentage and a positive sign," Roh said.

"This is about switchers from other brands, not Samsung Galaxy device users switching to another Galaxy device," Roh said.

Apple has filed several patents for foldable-display technology, but has yet to indicate any plans to release a device.

The Herald is angling to review the Fold4 shortly. The New York Times' Wirecutter said of its predecessor, the Fold3, "With its 7.6-inch folding OLED panel (plus Samsung's first under-display selfie camera), is undoubtedly the most capable Android phone in the world. You can run multiple apps side by side and multitask more efficiently than you can on any regular phone. However, its price tag is far too steep for most people. It's also huge and heavy."

The Fold4 is little lighter (263g to the Fold3's 271g), and marginally thinner at 15.8mm to the 3's mm 16.0mm folded.

Most upgrades are incremental, bar a big-bang camera upgrade.

where the Fold3 had a triple 12MP camera system, Samsung, the Fold4 features a 50MP wide sensor, alongside a 10MP telephoto and a 12MP ultra-wide in the Galaxy Z Fold4.

As well as being sharper, the Fold4's new main camera lets in 23 per cent more light, making it better for darker shooting situations.

The Flip4 is also a case of tweaks and refinements, but does feature a noticeably larger battery 370mAh0 to the Flip3's 3300mAh and adds support for 25W fast charging. Its second major upgrade is a faster processor, the Snapdragon 8+ Gen 1.

See full Flip4 tech spes here, and Fold4 tech specs here.