IBIT vs FBTC: Which Spot Bitcoin ETF Is Better
IBIT and FBTC have the same 0.25% fee, same access, similar tracking. The decision comes down to one thing: custody. Here is the full side-by-side.
TL;DR. IBIT and FBTC are the two largest US spot Bitcoin ETFs, both charging 0.25%, both available everywhere, both producing tracking error within 25 bp of spot bitcoin. The structural difference: IBIT is custodied by Coinbase Custody Trust (the dominant choice, ~80% of category AUM); FBTC is custodied in-house by Fidelity Digital Assets. Pick IBIT for liquidity and platform dominance. Pick FBTC for custody diversification away from Coinbase. Many serious allocators hold both.
The headline comparison
| Dimension | IBIT | FBTC |
|---|---|---|
| Issuer | BlackRock | Fidelity |
| Custodian | Coinbase Custody Trust | Fidelity Digital Asset Services (in-house) |
| Expense ratio | 0.25% | 0.25% |
| AUM (Apr 2026) | ~$70 billion | ~$22 billion |
| Average daily volume | ~30M shares ($1.2B notional) | ~8M shares ($320M) |
| Bid-ask spread | 1–2 bp | 2–3 bp |
| 30-day avg premium/discount | ±4 bp | ±5 bp |
| One-year tracking error vs BTC | −15 bp | −18 bp |
| Inception | 11 Jan 2024 | 11 Jan 2024 |
The custody question
This is the most-discussed differentiator and the most consequential. Roughly 80% of US spot Bitcoin ETF category AUM sits at Coinbase Custody — including IBIT. FBTC is one of the three mainstream alternatives (the others: HODL at Gemini, BRRR at a smaller custodian).
The Coinbase concentration is not a one-day risk but a category-level systemic exposure. A catastrophic operational failure at Coinbase Custody — a regulatory shutdown, an unprecedented hack, a sanctions-related freeze — would touch IBIT alongside 7 other major funds simultaneously. FBTC's in-house Fidelity Digital Assets custody is the cleanest diversifier.
The counterargument: Fidelity Digital Assets is also a Fidelity company. The sponsor (Fidelity Service Company) and custodian (Fidelity Digital Asset Services) are both under FMR LLC. If you specifically want sponsor-and-custodian independence (not just non-Coinbase), HODL on Gemini is the cleanest answer — see VanEck HODL review.
Full custody background in how Bitcoin ETF custody actually works.
Liquidity and execution
IBIT trades roughly 4× the daily volume of FBTC. For typical retail order sizes (under $50k) the difference is invisible — both products fill instantly with tight spreads. For institutional block orders ($1M+), IBIT's deeper book consistently delivers better execution.
On a $5M block buy, IBIT typically fills within 2 bp of mid; FBTC may show 4–5 bp of impact. On a $50M block, the gap is wider still. This is why pension funds and large RIAs default to IBIT.
Tracking quality
Both funds track bitcoin closely. The 2024 full-year tracking error metrics:
- IBIT: spot BTC return + 0.50% (NAV gains from interest on cash holdings, residual rebalancing) − 0.25% (fee) − 0.05% (frictional) = NAV tracked roughly 0.05% above bitcoin's pure spot return after fee, and the share price tracked within 15 bp of NAV.
- FBTC: similar profile, slightly higher friction due to smaller volume → 18 bp behind theoretical perfect tracking.
The 3 bp gap is real but small. Over a 10-year hold on a $100k position it accumulates to roughly $300 of foregone return — meaningful at very large positions, immaterial at retail scale.
Holders
13F filings show different institutional holder mixes:
- IBIT: Hightower, Cetera, Edelman (wealth managers), Wisconsin/Michigan pensions, Millennium/Citadel (arb funds), large family offices. The institutional default.
- FBTC: Heavier in Fidelity's wealth-management ecosystem, FidelityCharitable, corporate treasuries that already custody with Fidelity, fewer hedge funds.
Roughly 35% of FBTC institutional holders also hold IBIT — the cross-holding is real and increasing. Serious bitcoin allocators split exposure between the two as a custody-diversification practice.
The decision
Pick IBIT if you:
- Are an institutional allocator prioritising liquidity.
- Have an existing BlackRock / iShares relationship.
- Want the safest brand default.
- Need maximum tracking quality at large position sizes.
Pick FBTC if you:
- Specifically want custody diversification away from Coinbase.
- Are an existing Fidelity customer consolidating accounts.
- Hold large concentrated retirement assets and prefer one of the most conservative US asset managers.
Hold both if you:
- Have a meaningful position (>$100k typical threshold) and want true custody diversification.
- Are managing a portfolio for clients where single-issuer risk is a concern.
- Want flexibility for tax-loss harvesting between the two — see tax-loss harvesting.
FAQ
Which Bitcoin ETF is bigger, IBIT or FBTC?
IBIT (BlackRock iShares) is roughly 3× larger than FBTC (Fidelity), with approximately $70 billion AUM vs $22 billion as of April 2026. Both are the dominant products in the US spot Bitcoin ETF category.
Is IBIT's fee lower than FBTC's?
No — both charge 0.25% expense ratio. IBIT had an initial waiver (0.12% on the first $5B for 12 months) which expired in January 2025. FBTC did not offer a launch waiver; the headline 0.25% has applied since inception.
Should I hold both IBIT and FBTC?
For meaningful positions (typically $100k+), yes — splitting between the two diversifies custody risk (Coinbase Custody vs Fidelity Digital Assets) while maintaining the same fee and similar tracking. Many institutional allocators do this.
Is FBTC safer than IBIT?
Different risks rather than safer. FBTC removes Coinbase Custody concentration exposure (real category-level risk). IBIT has more institutional-weight operational risk management behind it (BlackRock's scale). Neither has experienced a custody issue since launch.
What's the main difference between IBIT and FBTC for retail investors?
For retail investors with positions under $100k, the practical difference is small — same fee, same tax treatment, same broker access, similar tracking. The Coinbase vs Fidelity custody question is the one structural differentiator that may matter on principle.
Sources and further reading
- BlackRock iShares Bitcoin Trust prospectus — sec.gov.
- Fidelity Wise Origin Bitcoin Fund prospectus — sec.gov.
- Internal: BlackRock IBIT review, Fidelity FBTC review, Custody mechanics.
