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Side-by-side financial comparison of CASTLE BIOSCIENCES INC (CSTL) and Fastly, Inc. (FSLY). Click either name above to swap in a different company.
Fastly, Inc. is the larger business by last-quarter revenue ($172.6M vs $87.0M, roughly 2.0× CASTLE BIOSCIENCES INC). On growth, Fastly, Inc. posted the faster year-over-year revenue change (22.8% vs 0.8%). CASTLE BIOSCIENCES INC produced more free cash flow last quarter ($19.7M vs $12.2M). Over the past eight quarters, Fastly, Inc.'s revenue compounded faster (13.7% CAGR vs 9.2%).
Castle Biosciences Inc. is a commercial-stage diagnostic firm that develops and markets proprietary, clinically actionable tests for dermatological conditions such as melanoma and other skin cancers, plus rare diseases. It operates mainly in the U.S. healthcare market, focusing on segments with high unmet need for more accurate diagnostics to guide treatment choices.
Fastly, Inc. is an American company based in San Francisco, which describes itself as a cloud computing company. Fastly provides content delivery network services, image optimization, and load balancing services. Fastly's cloud security services include denial-of-service attack protection, bot mitigation, and a web application firewall.
CSTL vs FSLY — Head-to-Head
Income Statement — Q4 FY2025 vs Q4 FY2025
| Metric | | |
|---|---|---|
| Revenue | $87.0M | $172.6M |
| Net Profit | — | $-15.5M |
| Gross Margin | 79.0% | 61.4% |
| Operating Margin | -4.4% | -8.7% |
| Net Margin | — | -9.0% |
| Revenue YoY | 0.8% | 22.8% |
| Net Profit YoY | — | 52.9% |
| EPS (diluted) | $-0.06 | $-0.10 |
Green = leading value per metric. Periods may differ when fiscal calendars don't align.
8-Quarter Revenue & Profit Trend
Side-by-side quarterly history. Quarters aligned by calendar period so offset fiscal years line up.
| Q4 25 | $87.0M | $172.6M | ||
| Q3 25 | $83.0M | $158.2M | ||
| Q2 25 | $86.2M | $148.7M | ||
| Q1 25 | $88.0M | $144.5M | ||
| Q4 24 | $86.3M | $140.6M | ||
| Q3 24 | $85.8M | $137.2M | ||
| Q2 24 | $87.0M | $132.4M | ||
| Q1 24 | $73.0M | $133.5M |
| Q4 25 | — | $-15.5M | ||
| Q3 25 | $-501.0K | $-29.5M | ||
| Q2 25 | $4.5M | $-37.5M | ||
| Q1 25 | $-25.8M | $-39.1M | ||
| Q4 24 | — | $-32.9M | ||
| Q3 24 | $2.3M | $-38.0M | ||
| Q2 24 | $8.9M | $-43.7M | ||
| Q1 24 | $-2.5M | $-43.4M |
| Q4 25 | 79.0% | 61.4% | ||
| Q3 25 | 77.5% | 58.4% | ||
| Q2 25 | 79.5% | 54.5% | ||
| Q1 25 | 81.4% | 53.2% | ||
| Q4 24 | 81.3% | 53.4% | ||
| Q3 24 | 81.8% | 54.5% | ||
| Q2 24 | 83.3% | 55.1% | ||
| Q1 24 | 81.0% | 54.8% |
| Q4 25 | -4.4% | -8.7% | ||
| Q3 25 | -8.2% | -18.2% | ||
| Q2 25 | -4.9% | -24.8% | ||
| Q1 25 | -31.7% | -26.4% | ||
| Q4 24 | 4.7% | -24.4% | ||
| Q3 24 | 5.9% | -29.6% | ||
| Q2 24 | 5.8% | -35.3% | ||
| Q1 24 | -7.5% | -34.6% |
| Q4 25 | — | -9.0% | ||
| Q3 25 | -0.6% | -18.6% | ||
| Q2 25 | 5.2% | -25.2% | ||
| Q1 25 | -29.4% | -27.1% | ||
| Q4 24 | — | -23.4% | ||
| Q3 24 | 2.6% | -27.7% | ||
| Q2 24 | 10.3% | -33.0% | ||
| Q1 24 | -3.5% | -32.5% |
| Q4 25 | $-0.06 | $-0.10 | ||
| Q3 25 | $-0.02 | $-0.20 | ||
| Q2 25 | $0.15 | $-0.26 | ||
| Q1 25 | $-0.90 | $-0.27 | ||
| Q4 24 | $0.32 | $-0.23 | ||
| Q3 24 | $0.08 | $-0.27 | ||
| Q2 24 | $0.31 | $-0.32 | ||
| Q1 24 | $-0.09 | $-0.32 |
Balance Sheet & Financial Strength
Snapshot of each company's liquidity, leverage and book value from the latest quarter.
| Metric | | |
|---|---|---|
| Cash + ST InvestmentsLiquidity on hand | $299.5M | $361.8M |
| Total DebtLower is stronger | $10.1M | — |
| Stockholders' EquityBook value | $470.9M | $929.6M |
| Total Assets | $578.6M | $1.5B |
| Debt / EquityLower = less leverage | 0.02× | — |
8-quarter trend — quarters aligned by calendar period.
| Q4 25 | $299.5M | $361.8M | ||
| Q3 25 | $287.5M | $342.9M | ||
| Q2 25 | $275.9M | $321.2M | ||
| Q1 25 | $275.2M | $307.3M | ||
| Q4 24 | $293.1M | $295.9M | ||
| Q3 24 | $95.0M | $308.2M | ||
| Q2 24 | $85.6M | $311.8M | ||
| Q1 24 | $82.9M | $329.5M |
| Q4 25 | $10.1M | — | ||
| Q3 25 | $10.0M | — | ||
| Q2 25 | $10.0M | — | ||
| Q1 25 | $10.0M | — | ||
| Q4 24 | $10.0M | — | ||
| Q3 24 | $10.0M | — | ||
| Q2 24 | $10.0M | — | ||
| Q1 24 | $10.0M | — |
| Q4 25 | $470.9M | $929.6M | ||
| Q3 25 | $467.0M | $937.0M | ||
| Q2 25 | $455.4M | $942.6M | ||
| Q1 25 | $440.3M | $957.0M | ||
| Q4 24 | $455.8M | $965.3M | ||
| Q3 24 | $441.1M | $969.5M | ||
| Q2 24 | $423.9M | $981.2M | ||
| Q1 24 | $402.5M | $991.8M |
| Q4 25 | $578.6M | $1.5B | ||
| Q3 25 | $562.8M | $1.5B | ||
| Q2 25 | $544.7M | $1.5B | ||
| Q1 25 | $501.7M | $1.4B | ||
| Q4 24 | $531.2M | $1.5B | ||
| Q3 24 | $514.6M | $1.5B | ||
| Q2 24 | $487.3M | $1.5B | ||
| Q1 24 | $458.5M | $1.5B |
| Q4 25 | 0.02× | — | ||
| Q3 25 | 0.02× | — | ||
| Q2 25 | 0.02× | — | ||
| Q1 25 | 0.02× | — | ||
| Q4 24 | 0.02× | — | ||
| Q3 24 | 0.02× | — | ||
| Q2 24 | 0.02× | — | ||
| Q1 24 | 0.02× | — |
Cash Flow & Capital Efficiency
How much cash each business actually produces after reinvestment. Cash flow is harder to manipulate than net income.
| Metric | | |
|---|---|---|
| Operating Cash FlowLast quarter | $26.9M | $22.4M |
| Free Cash FlowOCF − Capex | $19.7M | $12.2M |
| FCF MarginFCF / Revenue | 22.7% | 7.1% |
| Capex IntensityCapex / Revenue | 8.3% | 5.9% |
| Cash ConversionOCF / Net Profit | — | — |
| TTM Free Cash FlowTrailing 4 quarters | $28.3M | $65.8M |
8-quarter trend — quarters aligned by calendar period.
| Q4 25 | $26.9M | $22.4M | ||
| Q3 25 | $22.6M | $28.9M | ||
| Q2 25 | $20.8M | $25.8M | ||
| Q1 25 | $-6.0M | $17.3M | ||
| Q4 24 | $24.4M | $5.2M | ||
| Q3 24 | $23.3M | $5.0M | ||
| Q2 24 | $24.0M | $-4.9M | ||
| Q1 24 | $-6.8M | $11.1M |
| Q4 25 | $19.7M | $12.2M | ||
| Q3 25 | $7.8M | $22.9M | ||
| Q2 25 | $11.6M | $15.9M | ||
| Q1 25 | $-10.8M | $14.7M | ||
| Q4 24 | $16.8M | $251.0K | ||
| Q3 24 | $17.0M | $3.0M | ||
| Q2 24 | $18.8M | $-6.7M | ||
| Q1 24 | $-16.0M | $9.5M |
| Q4 25 | 22.7% | 7.1% | ||
| Q3 25 | 9.4% | 14.5% | ||
| Q2 25 | 13.4% | 10.7% | ||
| Q1 25 | -12.2% | 10.2% | ||
| Q4 24 | 19.5% | 0.2% | ||
| Q3 24 | 19.8% | 2.2% | ||
| Q2 24 | 21.6% | -5.1% | ||
| Q1 24 | -21.9% | 7.1% |
| Q4 25 | 8.3% | 5.9% | ||
| Q3 25 | 17.9% | 3.8% | ||
| Q2 25 | 10.7% | 6.6% | ||
| Q1 25 | 5.4% | 1.8% | ||
| Q4 24 | 8.8% | 3.5% | ||
| Q3 24 | 7.4% | 1.5% | ||
| Q2 24 | 6.0% | 1.3% | ||
| Q1 24 | 12.5% | 1.2% |
| Q4 25 | — | — | ||
| Q3 25 | — | — | ||
| Q2 25 | 4.60× | — | ||
| Q1 25 | — | — | ||
| Q4 24 | — | — | ||
| Q3 24 | 10.29× | — | ||
| Q2 24 | 2.69× | — | ||
| Q1 24 | — | — |
Financial Flow Comparison
Revenue → gross profit → operating profit → net profit for each company.
Revenue Breakdown by Segment
CSTL
| Dermatologic | $48.6M | 56% |
| Non Dermatologic | $38.4M | 44% |
FSLY
| Network Services | $130.8M | 76% |
| Security | $35.4M | 21% |
| Other | $6.4M | 4% |
