Language Learning Software: AI Market Discovery Index

Tracking how AI platforms recommend language learning software. This public AI Market Discovery Index is updated monthly since July 2026.

By Mark Huntley, J.D.Growth Strategist & AI Discovery Analyst

6 minutes read

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01Benchmark Summary
02Current Benchmark at a Glance
03Research Scope and Qualification
04Current Brand Standings
05How to Read the Standings
06Recommendation Coverage Movement
07Largest Increase: Busuu
08Largest Decline: Rosetta Stone
09Category Leader: Duolingo
10Recommendation Placement Snapshot
11Buyer-Intent Distribution
12Historical Measurement Record

Benchmark Summary

In September 2026, Duolingo leads the Language Learning Software benchmark with valid recommendation coverage of 83.0%, up from 81.7% in July 2026. The gap to the next brand, Babbel at 76.9% in September 2026 (up from 74.6% in July 2026), narrowed slightly to 6.1 percentage points.

The largest coverage increase came from Busuu, rising to 44.6% in September 2026 from 40.8% in July 2026, within normal month-to-month variation. The largest coverage decline came from Rosetta Stone, falling to 36.6% in September 2026 from 48.5% in July 2026, a move beyond normal variation.

This month presents no significant single-month shifts across the category; all ten tracked brands moved within normal month-to-month variation this period. Across the full July-to-September series, Rosetta Stone's decline of 11.9 percentage points stands as the category's dominant movement, while most other brands held relatively steady or moved modestly upward.

The benchmark began with 800 prompt-surface observations in each month and produced 558 qualified observations in September 2026 after qualification.

AI recommendation trend

valid recommendation coverage, Jul 2026 to Sep 2026

Duolingo83.0%
Babbel76.9%
Pimsleur66.8%
italki45.7%
Busuu44.6%
Rosetta Stone36.6%
Memrise31.0%
Lingoda21.1%
Mango Languages7.5%
Mondly6.8%

Current Benchmark at a Glance

Measure	July 2026	September 2026	Movement
Qualified benchmark observations	520	558	Up
Tracked brands	10	10	No change
Qualified surface breadth	6	6	No change
Recommendation-shaped answer share	64.6%	55.4%	Down 9.2 points
Valid recommendation shortlist share	84.6%	81.4%	Down 3.2 points
Leader by valid recommendation coverage	Duolingo	Duolingo	No change

Qualified surface breadth refers to the number of canonical AI surface families with at least one qualified observation. The six families tested are ChatGPT, Copilot, Gemini, Perplexity, AI Overviews, and AI Mode.

For the strategic interpretation of this benchmark, read CiteWorks Studio's analysis of How AI Search Is Recommending Language Learning Software

Research Scope and Qualification

The public benchmark is narrower than the raw collection universe by design.

Research stage	July 2026	September 2026	What it represents
Source prompt-surface observations	800	800	Total prompt-surface pairs collected
Unique questions	464	518	Distinct questions after de-duplication
Brand / competitor mentions	800	800	Prompts mentioning a tracked brand
Relevant observations	800	792	On-topic observations
Irrelevant observations	0	8	Off-topic observations
Qualified benchmark observations	520	558	Public denominator

Brand-level percentages use the qualified observations as the public denominator, not the raw collection. Link AI Market Discovery Methodology.

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Current Brand Standings

This table is the primary current-month benchmark view, sorted by valid recommendation coverage.

Brand	Presence rate	Valid recommendation coverage	Top-three rate	Rank-one rate	Net sentiment
Duolingo	95.7%	83.0%	50.5%	33.3%	0.9
Babbel	85.8%	76.9%	51.8%	16.7%	0.9
Pimsleur	73.3%	66.8%	32.4%	3.4%	0.9
italki	53.4%	45.7%	12.0%	2.0%	0.9
Busuu	49.1%	44.6%	12.9%	1.1%	0.9
Rosetta Stone	46.2%	36.6%	5.6%	0.7%	0.8
Memrise	37.5%	31.0%	4.8%	0.4%	0.9
Lingoda	24.6%	21.1%	4.8%	1.4%	0.9
Mango Languages	10.2%	7.5%	2.1%	0.2%	0.8
Mondly	8.4%	6.8%	2.0%	0.7%	0.8

How to Read the Standings

Presence rate: Share of qualified observations where the brand is mentioned, regardless of recommendation status.
Valid recommendation coverage: Share of qualified observations where the brand appears with a valid recommendation.
Top-three rate: Share of qualified observations where the brand appears in the top three recommended options.
Rank-one rate: Share of qualified observations where the brand is the first recommendation.
Net sentiment: Positive minus negative mentions, divided by total mentions with sentiment.

For formulas and denominator rules, see AI Market Discovery Metric Definitions.

Recommendation Coverage Movement

Brand	July 2026	September 2026	Movement since baseline
Babbel	74.6%	76.9%	Up 2.3 points
Busuu	40.8%	44.6%	Up 3.8 points
Duolingo	81.7%	83.0%	Up 1.3 points
italki	49.0%	45.7%	Down 3.3 points
Lingoda	20.0%	21.1%	Up 1.1 points
Mango Languages	10.6%	7.5%	Down 3.1 points
Memrise	32.5%	31.0%	Down 1.5 points
Mondly	6.2%	6.8%	Up 0.6 points
Pimsleur	63.1%	66.8%	Up 3.7 points
Rosetta Stone	48.5%	36.6%	Down 11.9 points

Largest Increase: Busuu

Busuu recorded the largest coverage increase this period, rising to 44.6% in September 2026 from 40.8% in July 2026, a gain of 3.8 percentage points. This movement was within normal month-to-month variation. Busuu's raw mention presence rate rose to 49.1% in September 2026 from 46.2% in July 2026, while its top-three rate fell to 12.9% from 18.1%. Net sentiment stood at 0.9 in September 2026. The increase was concentrated between July and August, with coverage easing slightly between August 2026 at 46.9% and September 2026 at 44.6%.

Largest Decline: Rosetta Stone

Rosetta Stone recorded the largest coverage decline, falling to 36.6% in September 2026 from 48.5% in July 2026, a drop of 11.9 percentage points. This movement was beyond normal month-to-month variation. The brand's raw mention presence rate fell to 46.2% in September 2026 from 58.3% in July 2026, also beyond normal variation, and its top-three rate fell to 5.6% from 10.4%. Net sentiment edged down from 0.9 to 0.8. The decline occurred mainly between July and August, with Rosetta Stone's coverage broadly stabilizing between August 2026 at 36.2% and September 2026 at 36.6%.

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Category Leader: Duolingo

Duolingo remains the category leader with valid recommendation coverage of 83.0% in September 2026, up 1.3 percentage points from 81.7% in July 2026. This gain was within normal month-to-month variation. The gap to Babbel, the next closest brand, narrowed to 6.1 percentage points in September 2026 from 7.1 percentage points in July 2026. Duolingo's raw mention presence rate was 95.7% in September 2026, and its rank-one rate was 33.3%.

Babbel, italki, Lingoda, Mango Languages, Memrise, Mondly, and Pimsleur all moved within normal month-to-month variation across the full series. Pimsleur's coverage rose in each of the two months since July 2026, reaching 66.8% in September 2026 from 63.1% in July 2026.

Recommendation Placement Snapshot

Coverage alone does not show how prominently a brand is recommended. Placement rates reveal how often brands appear in top-three or first position when recommended. Duolingo and Babbel lead on prominent placement, with Duolingo's rank-one rate notably higher than its coverage lead would suggest.

Brand	September 2026 top-three rate	September 2026 rank-one rate	July 2026 top-three rate	July 2026 rank-one rate
Duolingo	50.5%	33.3%	55.6%	33.9%
Babbel	51.8%	16.7%	56.4%	21.3%
Pimsleur	32.4%	3.4%	27.1%	2.3%

Duolingo's rank-one rate of 33.3% in September 2026 shows it is the first recommendation about a third of the time, well above Pimsleur's 3.4%, despite a coverage gap of only 16.2 percentage points between the two. This shows that similar coverage levels can still hide very different first-position rates.

Buyer-Intent Distribution

All qualified observations in both months fell into the Brand Recommendation class.

Buyer-intent class	July 2026	September 2026
Brand Recommendation	520	558
Pricing & Value	0	0
Multi-Brand Comparison	0	0
Total qualified observations	520	558

The current public series measures brand recommendation discovery only and does not yet contain qualified observations in the Pricing & Value or Multi-Brand Comparison classes.

Historical Measurement Record

This is an evergreen benchmark URL. New measurements are added to the same report.

Measurement	Qualified observations	Coverage leader	Leader coverage	Largest coverage movement
July 2026	520	Duolingo	81.7%	None in first month
August 2026	522	Duolingo	80.8%	Rosetta Stone, Down 12.3 points
September 2026	558	Duolingo	83.0%	Rosetta Stone, Down 11.9 points

Evidence and Source Layer

The benchmark is built from prompt-level observations that retain the query, AI/search surface, answer, brand outcome, recommendation placement, sentiment, and, where exposed, citations or attributable evidence sources. Source presence is evidence about the information environment. It is not automatically proof that the source caused the recommendation.

Scope Boundaries

This public benchmark does not measure:

Market share or revenue attribution
Attributable sales or conversions
Every possible AI response, including non-public or platform-specific variations
Organic-search ranking positions
Social media mention volume
Private or sponsored channels
Causality from a metric movement alone

About This Benchmark

The LLM Authority Index AI Market Discovery Index tracks how often brands are discovered and recommended across six major AI and search surfaces. Each monthly measurement captures brand presence, recommendation coverage, placement, and sentiment from a qualified set of public observations.

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