Indus Script: The Undeciphered Writing of the Harappans

The Indus script is the writing system of the Indus Valley Civilisation, used mainly between about 2600 and 1900 BC on seals, tablets and pottery. Around 4,000 inscriptions survive, yet no one has been able to read them, and the language they record is unknown. It is one of the most famous undeciphered scripts in the world and the biggest obstacle to understanding the Harappan civilisation.

Where the script is found

Most Indus inscriptions appear on small square stamp seals carved from steatite, a soft stone that was hardened by firing. A typical seal is two to three centimetres across and shows an animal beneath a short line of signs. The seals were carved in reverse so that pressing them into clay produced a readable impression, and clay sealings found at several sites show they were used to mark goods or containers.

The script also appears on small moulded tablets of clay and faience, on copper tablets from Mohenjo-daro, on bangles, on tools and scratched or painted on pottery. Inscribed objects have been found from Balochistan to Gujarat and Haryana, and Indus seals have turned up in the Persian Gulf and in Mesopotamian cities such as Ur and Kish, evidence of long-distance trade.

Alexander Cunningham published the first Indus seal from Harappa in 1875, without knowing what it was. Only after the excavations of the 1920s was the script recognised as belonging to a Bronze Age civilisation.

What the inscriptions look like

Indus texts are extremely short. The average inscription has about five signs, and most have fewer than ten. The longest text on a single surface contains about 17 signs, while one multi-sided object carries around 26.

Scholars count between about 400 and more than 600 different signs, depending on how they classify variants. That is far too many for an alphabet, which typically has 20 to 40 letters, and too few for a purely word-based system like Chinese. Most specialists therefore think it was a logo-syllabic script, combining signs for whole words with signs for sounds, similar in principle to cuneiform or Egyptian hieroglyphs.

The direction of writing is usually right to left. Signs are often squeezed together at the left end of a line, and where strokes overlap the later stroke shows the order of writing. A few texts continue onto a second line in the opposite direction.

The earliest possible forerunners of the script are marks scratched on pottery at Harappa from before about 3300 BC. The fully developed script appears around 2600 BC and fell out of use after about 1900 BC, as the Indus cities declined.

Famous seals and inscriptions

The most common seal motif is an animal resembling a bull with a single horn, usually called the “unicorn”. It is often shown standing before an object that some identify as a cult stand or incense burner. Other seals show zebu bulls, elephants, tigers, rhinoceroses and water buffalo.

The so-called Pashupati seal, found at Mohenjo-daro in the late 1920s, shows a figure with a large horned headdress seated in a yoga-like posture and surrounded by animals. John Marshall called it a “proto-Shiva”, linking it to the Hindu god Shiva in his aspect as Pashupati, “lord of animals”. Many scholars now regard this identification as uncertain.

At Dholavira in Gujarat, excavators in the early 1990s found ten large signs, each about 37 centimetres high, made of white inlaid material that probably once decorated a wooden board near a gateway. This “signboard” is the largest known Indus inscription and suggests the script was sometimes meant to be seen in public.

What the texts might say

Even without a decipherment, the context of the inscriptions offers clues. Because seals were used to stamp clay sealings on goods, many scholars think their short texts record names, titles or offices of owners, much like seals in Mesopotamia. Certain signs occur again and again at the end of texts, and some researchers interpret these as grammatical endings or as titles.

Moulded tablets from Harappa often carry identical inscriptions, made from the same mould, and may have been tokens, receipts or amulets rather than records. Inscriptions on pottery and bangles could mark ownership or contents.

There is no evidence of long Indus texts such as literature, laws or chronicles, although such writings could have existed on perishable materials such as palm leaves, cloth or wood that have not survived. This is one reason why the question of how widely writing was used in Indus society remains open.

Attempts at decipherment

Since the 1920s more than 100 decipherments have been proposed. Serious scientific work began in the 1960s, when a Soviet team led by Yuri Knorozov, who had contributed to deciphering Maya script, and a Finnish team including Asko Parpola independently used computer analysis of sign patterns. Both concluded that the language was probably an early form of Dravidian.

Iravatham Mahadevan published a concordance of the texts in 1977, and Parpola and colleagues have published the multi-volume Corpus of Indus Seals and Inscriptions since 1987. These works allow researchers to study patterns such as which signs appear at the beginning or end of texts and which occur together.

Other researchers have argued for Indo-Aryan, related to Sanskrit, or for other language families. One much-publicised claim in 2000 relied on a seal said to show a horse; the scholars Michael Witzel and Steve Farmer showed that it was a damaged unicorn seal whose image had been altered. In 2004 Farmer, Richard Sproat and Witzel went further, arguing that the signs were not writing in the full sense but a system of non-linguistic symbols. A statistical study led by Rajesh Rao in 2009 argued that the sign sequences show language-like structure, and the debate continues.

Why it is so hard to read

Successful decipherments usually depend on three things: a large body of texts, a known related language and a bilingual inscription. The Rosetta Stone opened Egyptian hieroglyphs because it repeated a text in Greek. The Indus script has none of these advantages.

The texts are short, many may be names or titles, and no bilingual text in the Indus script and a known script such as Akkadian cuneiform has been found. The language of the Harappans is unknown and may have no surviving descendants. In this respect the Indus script resembles other unread Bronze Age scripts such as Linear A of Crete.

Interest remains strong. In 2025 the government of the Indian state of Tamil Nadu announced a prize of one million US dollars for a convincing decipherment.

Timeline

• c. 3300 BC: Early marks on pottery at Harappa, possible forerunners of the script.
• c. 2600 BC: The mature Indus script appears on seals and tablets.
• c. 1900 BC: Use of the script declines as the Indus cities shrink.
• 1875: Alexander Cunningham publishes the first known Indus seal.
• 1920s: Excavations at Harappa and Mohenjo-daro reveal hundreds of inscribed seals.
• 1960s: Soviet and Finnish teams begin computer analysis of the script.
• 1977: Iravatham Mahadevan publishes his concordance of Indus texts.
• 1987: First volume of the Corpus of Indus Seals and Inscriptions appears.

Why it matters

The Indus script is the voice of the Indus Valley Civilisation, but that voice is still silent. Reading it could reveal the names, language, beliefs and government of one of the world’s first urban societies. Until a breakthrough comes, it stands as a reminder of how much of the human past can be lost when writing can no longer be understood.