Security thread

{{short description|Security feature of banknotes}}

{{More citations needed|date=September 2024}}

File:US $20 under blacklight.jpg, glowing under a blacklight]]

File:Benang pengaman, tinta OVI, dan tanda air pada uang Rp50,000 dan Rp100,000 emisi 2022.jpg and Rp50,000 notes issued in 2022]]

A security thread is a security feature of many banknotes to protect against counterfeiting. Introduced in 1990, it consists of a thin ribbon that is woven through the note's paper.{{cite web| title=Secret service| url=http://www.secretservice.gov/money_design_features1990.shtml| url-status=dead| archiveurl=https://web.archive.org/web/20090118093705/http://www.secretservice.gov/money_design_features1990.shtml| archivedate=2009-01-18}}{{Cite web |title=Unsur-unsur Ini yang Bedakan Rupiah Asli dan Palsu – PID Polda Kepri |url=https://pid.kepri.polri.go.id/unsur-unsur-ini-yang-bedakan-rupiah-asli-dan-palsu/ |access-date=2024-09-05 |language=id}}

Usually, the ribbon runs vertically, and is "woven" into the paper, so that it at some places emerges on the front side and at the remaining places at the rear side of the paper. It is made of metal foil, but sometimes of plastic, and oftentimes it has some text or numbers (e.g., the denomination) engraved.

Threads are embedded within the paper fiber and can be completely invisible or have a star burst effect, where the thread appears to weave in and out of the paper when viewed from one side, while the thread will always appear as a solid line when held up to the light. Features can be built into the thread material e.g., microprinting on a transparent plastic thread or adding materials so they fluoresce under ultraviolet light.

The thread is a difficult feature to counterfeit, {{Citation needed span|date=September 2024|but some counterfeiters have been known to print a thin grey line or a thin line of varnish in the area of the thread.}}

Security threads can also be used as an anti-counterfeiting device in passports. Those are generally made of plastic and contain microprinting.