ONTO vs PDFS: Which Is the Better Buy in 2026?
Last updated August 2026
Short answer
ONTO is the larger of the two ($12.86B market cap): the incumbent the market prices for continued execution (26.00x forward earnings, beta 1.54). PDFS is the smaller challenger ($1.93B), priced similarly on forward earnings (29.69x): more room to run, but more to prove. The real question is which set of drivers you believe, and whether owning one (or both) leaves you over-concentrated.
ONTO vs PDFS: the tie-breaker metrics
Same yardstick, side by side (as of August 2026). Valuation lined up like this is most meaningful for two names in the same corner of the market, which these are. Figures are approximate; verify before investing.
| Metric | ONTO | PDFS | What it tells you |
|---|---|---|---|
| Market cap | $12.86B | $1.93B | Size. The larger name is the incumbent; the smaller has more room to grow and more to prove. |
| Forward P/E | 26.00 | 29.69 | Valuation on next year's expected earnings, the same yardstick for both. Lower is cheaper for that growth; higher means the market is paying up. |
| Trailing P/E | 120.27 | 256.06 | Valuation on the last 12 months. A big drop from trailing to forward means the market expects earnings to jump, so more growth is already in the price. |
| Beta | 1.54 | 1.63 | Volatility vs the market. Above 1 swings harder than the index; below 1 is steadier. Higher beta means bigger drawdowns to hold through. |
| Price vs 52-week range | 57% of range | 52% of range | Where today's price sits between the 52-week low and high. Near the high is momentum with less margin of safety; near the low is out of favor or a discount, depending on why. |
| Price / book | 6.03 | 6.56 | How much you pay over book value. Very high can signal an asset-light, high-return business or a rich price. |
Before you buy: how ONTO and PDFS affect your concentration
The metrics above tell you which is the marginally better business. The bigger risk for most people is not picking the slightly worse stock, it is over-concentrating. ONTO and PDFS share themes, so owning both, or adding either to what you already hold, can quietly push a large share of your portfolio into one bet.
This is the part a generic comparison page cannot answer, because it depends on what you own. Connect your brokerage and Walnut shows your real, combined ONTO and PDFS exposure, flags overlap with your existing positions, and tells you if adding one would tip you past a concentration you are comfortable with, read-only by default, with your login staying at your broker. Walnut is not an investment adviser.
What does Onto Innovation (ONTO) do?
Onto Innovation designs and builds inspection, metrology, lithography, and data-analysis systems that semiconductor manufacturers use to measure and check chips during production. It was formed from the 2019 merger of Rudolph Technologies and Nanometrics, and it competes in areas like thin-film and critical-dimension (OCD) metrology, macro defect inspection, and advanced packaging inspection. Its tools, including the Dragonfly inspection platform and the Atlas and newer G-series metrology systems, are used across advanced logic nodes, specialty devices, and the packaging steps that stitch AI accelerators and high-bandwidth memory (HBM) together.
What does PDF Solutions (PDFS) do?
PDF Solutions, based in Santa Clara and founded in 1991, sells software and engineering services that let semiconductor manufacturers and their supply chains connect, collect, and analyze data across design, equipment, manufacturing, and test. Its flagship Exensio platform and factory-connectivity products (including the Cimetrix equipment-communication software) are used to raise yield, catch defects earlier, and manage vast volumes of fab data. The company has steadily shifted from a project-based analytics vendor toward a recurring, platform-centric model, with roughly 89% of revenue described as recurring as of Q1 2026.
ONTO vs PDFS: how do they differ?
Both fit overlapping themes, but they are not interchangeable. The useful comparison is which set of drivers and risks you want exposure to.
- ONTO drivers: Advanced packaging and HBM; Advanced logic nodes.
- PDFS drivers: Platform shift and recurring revenue; Semiconductor complexity and data volumes.
Which fits which kind of investor
A faster-growing, richer-valued name usually swings harder, so it suits a longer horizon and a higher tolerance for volatility; a steadier, more cash-generative business suits a more conservative or income-minded investor. The honest test is which set of risks you could hold through a drawdown: Onto is a semiconductor capital-equipment company, so its revenue is cyclical and can drop sharply in a chip-spending downturn. For PDFS, customer concentration is a real risk, since a handful of large chipmakers can drive a meaningful share of revenue and any single contract change can swing results.
ONTO or PDFS: which should you pick?
Growth-minded investors who believe the theme has years to run tend to accept the richer multiple for more upside; value-minded investors lean toward the cheaper forward earnings and steadier profile. Pick ONTO if you believe its drivers more; PDFS if you believe its. Many investors hold both, but since they share themes, that is a concentrated bet, not diversification. Decide deliberately and check overlap. For the full detail, see the ONTO and PDFS guides.
ONTO vs PDFS: the full fundamentals
ONTO. Onto trades at a mid-cap valuation that reflects its growth exposure to AI packaging rather than a deep-value multiple. Gross margin has run in the roughly 50-56% range depending on mix, and management guided second-quarter 2026 revenue to $320-$330 million with non-GAAP EPS of about $1.65-$1.73. These figures are as of May 2026 and will change with each quarterly report.
PDFS. PDFS returned to GAAP profitability in Q1 2026, with non-GAAP diluted EPS of about $0.31 and recurring revenue near 89% of the total. Because reported GAAP net income is thin relative to the share price, the trailing price-to-earnings ratio has run very high (above 100x, and higher on some 2026 readings), so the stock is priced on growth and margin expansion rather than current earnings. Figures are approximate and as of the dates shown.
Headline figures (approximate, MAY 2026): ONTO shows revenue (ttm) ~$1.03 billion, fy2025 revenue ~$1.005 billion, q1 2026 revenue ~$292 million (record, ~+9.5% YoY), q1 2026 non-gaap eps ~$1.42; PDFS shows revenue (ttm) ~$231M, fy2025 revenue ~$219M (up ~22%), q1 2026 revenue ~$60.1M (up ~26%), gross margin ~72%.
The bottom line: ONTO vs PDFS
ONTO and PDFS are related but distinct: same themes, different businesses and risks. Neither wins in the abstract; the right pick is whichever thesis you actually believe, sized so you are not over-concentrated in one theme. Walnut can show your combined ONTO and PDFS exposure against your real portfolio. It is not an investment adviser.
Wondering how ONTO or PDFS fits the portfolio you already own? Walnut is an AI investing app that connects your brokerage read-only and answers questions like that about your actual holdings: overlap, concentration, and how each position tracks the S&P 500. Compare the best AI portfolio analyzers or see the best AI investing apps in 2026.
Investing in Onto Innovation with AI
Connect the broker you already use and ask Walnut's AI how ONTO fits what you actually hold: whether you own it already through a fund, what it would do to your concentration, and how it has tracked the S&P 500. Read-only by default, and you approve anything before it reaches your broker.
FAQ
What is the difference between ONTO and PDFS?
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Onto Innovation designs and builds inspection, metrology, lithography, and data-analysis systems that semiconductor manufacturers use to measure and check chips during production. PDF Solutions, based in Santa Clara and founded in 1991, sells software and engineering services that let semiconductor manufacturers and their supply chains connect, collect, and analyze data across design, equipment, manufacturing, and test. They show up together because they share investment themes, but they are different businesses, so the better fit depends on which thesis you are expressing.
Is ONTO or PDFS the better stock?
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Neither is universally better. ONTO is the larger incumbent; PDFS is the smaller challenger and looks pricier on forward earnings. Walnut is informational, not investment advice. Compare what each does, the tie-breaker metrics above, and the risks, then decide which fits your thesis and what you already own.
Which is cheaper, ONTO or PDFS?
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On forward P/E (as of August 2026), ONTO trades at 26.00x and PDFS at 29.69x, so ONTO is the cheaper of the two on next year's expected earnings. A lower multiple is not automatically the better buy: a richer valuation can be justified by faster growth, and a lower one can reflect real risk. Weigh the multiple against how fast each business is compounding.
Should you own both ONTO and PDFS?
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Because they share themes, owning both concentrates you in that theme. That can be intentional (a focused bet) or accidental (less diversification than it looks). Walnut can show your combined exposure across both, and whether adding either over-concentrates you, before you buy.
What are the risks of ONTO vs PDFS?
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ONTO: Onto is a semiconductor capital-equipment company, so its revenue is cyclical and can drop sharply in a chip-spending downturn. A large share of sales concentrates in a handful of leading-edge logic and memory customers, so a single customer's capex delay or push-out can move a quarter meaningfully. Its growth thesis leans heavily on AI-driven advanced packaging and HBM demand continuing, which could soften if AI infrastructure spending cools or memory pricing weakens. Gross margin has fluctuated with product mix (it dipped year over year in early 2026 before guided recovery), and export controls on chip equipment sold into China add regulatory uncertainty. Larger, better-capitalized rivals like KLA can also pressure pricing and share. PDFS: Customer concentration is a real risk, since a handful of large chipmakers can drive a meaningful share of revenue and any single contract change can swing results. The business is exposed to the cyclical semiconductor capital-spending cycle, so a downturn in fab investment could slow bookings. Valuation is a standalone risk, as the stock trades at a very high GAAP price-to-earnings ratio (well over 100x at times in 2026), leaving little room for execution stumbles. The transition to a platform model is not guaranteed to keep expanding at recent rates, and competition from larger EDA and process-control vendors could pressure pricing. Finally, as a small-cap, PDFS shares can be volatile on single-quarter results.
Walnut is informational, not investment advice. This page is descriptive and not a recommendation to buy or sell ONTO or PDFS; figures are approximate and dated (as of August 2026). Verify current data before investing.