About This Site & Methodology

What this is

The Strait of Hormuz Ship Monitor is an independent, free dashboard that tracks commercial shipping through the Strait of Hormuz — the world's most important oil chokepoint — in near real time. It detects vessel crossings, estimates oil and gas export volumes, classifies transit routes, and flags sanctioned vessels, with historical charts for trend analysis.

It is built for anyone who needs a quick, factual read on what is physically moving through the strait: energy analysts, commodity traders, journalists, researchers, and the generally curious. It is not affiliated with any government, data vendor, or trading firm.

Why the Strait of Hormuz matters

The strait is a narrow waterway — about 21 nautical miles at its narrowest — connecting the Persian Gulf to the Gulf of Oman and the open ocean. Roughly a fifth of the world's petroleum and around a quarter of global liquefied natural gas trade passes through it. There is no meaningful seaborne alternative: pipeline detours can replace only a fraction of the flow. Ships transit through designated traffic-separation lanes, each just a few kilometers wide, making the strait uniquely sensitive to disruption — and making its daily traffic a leading indicator watched by energy markets worldwide.

Where the data comes from

Commercial vessels above certain size thresholds are required to broadcast their identity, position, course, and speed via AIS (Automatic Identification System) transponders. This site collects AIS position reports from publicly available sources approximately every 30 minutes, typically observing 1,800–2,000 vessels per cycle across the Persian Gulf, the strait itself, and the Gulf of Oman. Vessel characteristics (type, deadweight tonnage, flag, destination) come from the same public data, enriched with public ship registries.

Position history is retained for 90 days; detected crossings and daily aggregates are retained indefinitely.

How crossings are detected

The monitored area is divided into three zones: the Persian Gulf, the strait area (which also contains major anchorages such as Bandar Abbas and Qeshm), and the Gulf of Oman. A crossing is recorded when a vessel's observed track moves from one gulf to the other — whether we see it transit the strait fix by fix, or it disappears on one side and reappears on the other (common during coverage gaps and transponder dark periods; gaps of up to 15 days are tolerated before a reappearance is no longer linked).

Two refinements matter in practice:

• Anchorage calls. The Bandar Abbas / Qeshm anchorages sit inside the strait area. A vessel that arrives from the Gulf of Oman, dwells at anchor for more than 24 hours, and departs the way it came has still transited the strait's narrows twice; we count one crossing in the direction of the departure leg, provided its track actually crossed the narrows.
• Route classification. Completed transits are classified by which side of the strait they favored — the Oman-side or Iran-side lanes — where the track allows it; transits observed only as a disappearance/reappearance are labeled unidentified.

How the oil and gas estimates work

The headline export figures are capacity-based estimates, not measured cargoes:

applied to outbound tanker crossings only, split into crude (crude oil tankers) and products (oil products and oil/chemical tankers) by vessel category. LNG/LPG volumes are estimated analogously from gas-carrier crossings. Inbound tankers (typically in ballast) are counted as crossings but contribute nothing to export volumes.

Known limitations — read this before trading on the numbers

Honest measurement requires stating what this system cannot see:

1. AIS is self-reported and can be switched off. Sanctions-evading ("shadow fleet") vessels routinely go dark. Dark transits are invisible unless the vessel reappears within the linking window.
2. Electronic interference. Since mid-2025, GPS jamming and spoofing around the strait has intermittently degraded position quality for all vessels; during such periods (including the ongoing 2026 disruption), our figures should be read as conservative lower bounds. The jamming guide explains the mechanics.
3. Laden status is assumed, not observed. The DWT-based formula assumes outbound tankers are ~95% laden. Some are not; conversely, some cargo moves on vessels our category filter treats conservatively.
4. Category granularity. Public vessel-type data is imperfect; a small share of vessels is classified from partial information.
5. Coverage varies. Terrestrial AIS reception in parts of the strait fluctuates; the detection logic is designed to recover crossings from partial tracks, but no method recovers what was never observed.

For these reasons the site's figures are best used as a directionally reliable, methodologically consistent index of strait activity — ideal for spotting changes and trends — rather than as audited trade statistics.

Storage, supply and ship-to-ship analysis

Beyond the live tracker, the site maintains three analytical modules: oil storage, supply and demand, and STS Watch (beta). The first two draw on official statistics rather than AIS; STS Watch is built from our own AIS positions. Every figure carries its source and refresh date on the page.

• Oil storage. Reported inventory levels aggregated across countries: EIA weekly data for the United States (commercial crude, the Strategic Petroleum Reserve, gasoline, distillate, Cushing), the Petroleum Association of Japan and JODI for Japan (refiner stocks and the national strategic reserve), Eurostat for the EU27 (crude and total oil, with preliminary months summed from reporting member states), and JODI for Saudi Arabia, India, South Korea and the United Kingdom. Series in tonnes are converted at 7.33 bbl/t. Subset series are never stacked on their supersets. Collectors run daily; monthly sources typically lag one to three months.
• Supply and demand. World production and consumption, Gulf producers' output, OPEC and non-OPEC supply, OECD commercial stocks and days of cover, and US product consumption from the U.S. Energy Information Administration's Short-Term Energy Outlook (STEO), plus US crude imports from Persian Gulf countries from EIA's Petroleum Supply Monthly. STEO is re-downloaded daily; months after the latest observed month are EIA estimates and are always drawn dashed. The supply-shortfall decomposition (demand destruction, storage draw, foregone stock build) is an exact accounting identity on those series, not a model.
• Ship-to-ship transfers. An AIS-behaviour analysis of tankers that loiter in the Gulf of Oman without having transited the strait, pair-matched against crude tankers that went dark from a Persian Gulf position and resurfaced at the loiter spot. Volumes assume departures are laden at 95% of deadweight and are therefore upper bounds; matching is circumstantial evidence, not proof, and the underlying report is rebuilt daily from the last 90 days of positions. The full method is below.

All EIA products are U.S. government works in the public domain and are reproduced with attribution to the U.S. Energy Information Administration; JODI, PAJ and Eurostat data are used under their respective open-data terms.

STS Watch: how ship-to-ship transfers are estimated (beta)

STS Watch looks for oil that leaves the Gulf without ever showing up as a strait crossing. The pattern it tests for: a tanker crosses Hormuz with its AIS transponder off, meets a second tanker that is waiting in the Gulf of Oman with AIS on, and transfers its cargo ship-to-ship (STS). The second tanker then sails away looking like any other ship that never entered the Gulf. The page finds those waiting tankers (receivers), tries to pair each one with a tanker that went dark at the right time and place (a provider), and estimates how much oil the receivers could have carried away.

Step 1: candidate receivers

A receiver is a crude or product tanker that, within the 90 days of positions we keep:

• was seen in the Gulf of Oman;
• was never seen in the Persian Gulf or in the strait itself; and
• has no detected strait crossing in our records.

In other words, it had no visible way to load Gulf oil at a Gulf terminal.

Step 2: loitering away from a berth

For each candidate we look for loiter episodes: at least 48 hours spent within a 12 km radius, with a median speed of 2 knots or less, and positions in at least 40% of the half-hour polling slots (so a ship that simply went silent does not look stationary). Episodes at a port are dropped as ordinary port calls: within 12 km of Fujairah, Sohar, Muscat / Mina al Fahal or Sur / Qalhat, 10 km of Khor Fakkan, or 15 km of Iran's Jask terminal. A ship with at least one remaining episode counts as a receiver.

Step 3: what happened next

• Exited: after its last loiter the ship moved more than 25 km from the spot or reached 6 knots, and its latest position is outside the Gulf of Oman. The page labels where it went: toward India, the Arabian Sea, the Red Sea direction, or elsewhere.
• Went dark: no signal for more than four days after the loiter.
• In Gulf: still in the Gulf of Oman, staging or waiting.

Step 4: attribution

Each receiver gets one of three labels:

• STS match: a crude tanker that was in the Persian Gulf or the strait, and that has no detected crossing, went dark for at least 24 hours starting from a position west of the strait. Four conditions must all hold:
  • sailing from where it went dark at about 12 knots, it could have reached the loiter spot and still spent at least 12 hours there during the loiter;
  • its dark gap started and ended within the loiter window, give or take 24 hours;
  • it reappeared within 30 km of the loiter spot;
  • it did not reappear at a terminal's berths.
  Requiring the provider to have no detected crossing means its oil is not already counted in the dashboard's outbound figures. The 24-hour minimum gap and the reappearance test filter out the short gaps that GPS jamming produces for every ship.
• Jask: no STS match, but the ship loitered within 120 km of Iran's Jask pipeline terminal. That points to lifting from the Goreh–Jask pipeline, which also bypasses the strait.
• Unattributed: a receiver-like loiter with neither of the above.

Step 5: barrels

Volumes use the same capacity formula as the rest of the site:

It applies only to crude tankers of at least 25,000 DWT. Product tankers are listed as cases but carry no volume. An exited ship's volume is booked to the month its last loiter ended, and the monthly chart stacks those volumes by attribution. Ships still in the Gulf are summed as afloat capacity, and ships that went dark as dark capacity. Neither is counted as exported.

Reading the numbers

• Upper bounds. AIS does not report how much cargo a ship carries, so every departing receiver is assumed laden. Some leave partly loaded or empty.
• Circumstantial, not proof. Tankers also wait offshore for orders, bunkers, crew changes or a berth, especially off Fujairah. A match is a timing and geography pattern, and no label on the page is an allegation against a named vessel.
• What it cannot see. Transfers between two ships that both keep AIS off are invisible to this method.
• Rolling window. The report is rebuilt every day at 03:20 UTC from the last 90 days of positions, so the oldest month is partial and its total shrinks as positions age out.
• Separate from the headline. STS volumes are never added to the dashboard's outbound oil estimate. They are a separate, explicitly uncertain estimate of oil that may bypass the strait.

Each case on the page opens a map of its track: the approach in blue, the estimated STS window in orange, the exit transit in green, and the region's oil loading terminals for context.

Updates and availability

Data refreshes roughly every 30 minutes around the clock. Daily chart buckets use UTC. The underlying data is available through a free JSON API (see the API documentation) for research and non-commercial use.

Independence and contact

The site is operated independently. It carries advertising and may offer optional email updates to cover infrastructure costs; neither influences the data or methodology. Corrections, questions, and suggestions are welcome via the feedback form — the site improves regularly based on reader reports. See also our FAQ, the monthly crossing statistics, the explainer guides, and our Privacy Policy.

Nothing on this site is investment advice, and none of it should be used for navigation.