🚴🏼‍♂️ Strava Segment Comparator Extension 🏃🏼‍♀️

Chrome extension to compare two Strava activities by their segments. It can auto-detect activity tabs you already have open, read segment data from each activity, compute time and speed (or pace) deltas, and export the results as CSV. It runs entirely in your browser; no servers are involved.

If you have questions or issues, please open an issue on GitHub.

Features

• Auto-detect open Strava activity tabs: Scans your open tabs and auto-fills the first two activity URLs. Opening the popup does this quietly; the Auto-Detect button also says what it found
• Manual URL entry: Paste activity URLs if auto-detect isn’t used
• No tab flicker: If the activities are already open, they’re read in place; otherwise the page is fetched in the background. A hidden tab is only opened as a last resort, and is closed again even if you close the popup first
• Segment comparison: Matches segments by Strava's segment ID, so renamed segments still pair up and repeated efforts (laps, intervals) stay separate
• Time Diff %: Each time difference as a share of activity 1's time, so a short segment counts as much as a long one
• Copy summary: The summary as plain text on your clipboard, ready for a chat or club thread
• Summary strip: The net gap, the win/loss count, and the biggest losses and gains by name, above the table
• Swap activities: One click swaps activity 1 and 2. A comparison on screen is redone the other way round
• Sortable columns: Click a header to sort; click again to reverse
• Filter by name: Narrow a long ride to the segments you care about; the export follows what is shown
• Open in tab: Take the comparison out of the popup into a full-width tab, no refetching
• Rides and runs: Compares speed for rides and pace for runs, and normalizes across km/h vs mph and /km vs /mi. Runs no longer need to be open in a tab
• Power and heart rate: Average power and heart rate per segment and their deltas, each shown when either activity recorded it
• VAM: Metres climbed per hour on segments averaging 3% or steeper, and the delta
• Medals: Strava's own PR / 2nd / 3rd (and KOM) marker next to each effort's time
• Segment context: Distance and average grade under each segment name
• Personal records: One click adds your PR for each segment and how far off it you were. “Refresh my PRs” reads them again, skipping the day-long cache
• Your history: Where this effort ranks among all your efforts on the segment, with a sparkline of your times and your best marked — from the same lookup as the PRs, so it costs no extra requests
• Form: Reads each time change against the heart-rate change behind it — Fitness, Effort, Even, Easier, Slower or Fading
• Where the gap opened up: A bar per segment in course order showing the running total, so you can see whether the time went in one place or everywhere
• Overlapping segments: Segments that sit inside another are marked, and the summary can leave them out so no stretch of road is counted twice
• My Activities Here: Lists your other activities on activity 1's segments, most shared first; click one to compare against it
• Unmatched segments: Segments that only one activity has are listed rather than dropped
• Athlete-aware headers: Uses detected athlete names for table headers when available. When both activities are the same athlete's, they are labelled Activity 1 and Activity 2 instead
• Activity stats panels: Shows a side-by-side comparison of key activity stats, read from the page where possible and from Strava's embedded activity data when the page yields nothing
• CSV export: One-click export of the comparison table
• Persistent results: The last comparison is auto-restored on popup open
• Detailed logs: Built-in activity log with statuses and errors; quick Clear button

The comparison table is a plain, readable table, sortable by any column, with time and speed/pace deltas shown as both a colour and an arrow.

Install (Load Unpacked)

1. In Chrome, go to chrome://extensions/
2. Enable Developer mode
3. Click “Load unpacked” and select this project folder
4. Pin the extension (optional) and open it from the toolbar

Required permissions: storage, and host access to https://www.strava.com/* (see manifest.json). There is no tabs permission: host access already shows the extension the URLs of your Strava tabs, and no others.

Usage

Quick start (Auto-detection)

1. Open two Strava activity pages in separate tabs
2. Click the extension icon
3. Click “Auto-Detect” to populate the URLs
4. Click “Compare Activities”

Manual

1. Copy/paste two activity URLs into the input fields
2. Click “Compare Activities”

Swapping activities

Every delta is activity 2 minus activity 1, and the PR and history columns read activity 1's times, so which is which matters. The ⇄ button between the URL fields swaps them. If a comparison is showing, it is redone the other way round so the table matches the fields. That re-reads both activities, and any PR columns need “Compare vs my PRs” again, which comes from the cache.

My Activities Here

Fill in (or auto-detect) Activity 1 only, then click “My Activities Here”. It reads activity 1’s segments, looks up your effort history on each, and lists up to five of your other activities that share the most of them, with their date and how many segments they share. Click one to fill Activity 2 and compare.

• “Your” means the signed-in Strava athlete, so this also works when activity 1 is a friend’s ride: it finds your rides on the same segments
• Each segment’s history is one request, shared with “Compare vs my PRs” through a 24-hour cache, so running one makes the other free. Only your 20 most recent activities per segment are considered

Reading the summary

Above the table you get the net gap, how many segments each athlete took, and the biggest three losses and gains by name. The net is a plain sum of the per-segment deltas — the sense in which people say “I lost three minutes” — so a long segment contributes more to it than a short one. It is not weighted by segment length.

The Time Diff % column is the length-fair reading: each segment's time difference as a share of activity 1's time there. Ten seconds is 20% on a 50-second sprint and under 1% on a twenty-minute climb, so sorting by it puts the segments where activity 2 was relatively slowest on top.

“Copy summary” puts the same reading on your clipboard as plain text: who was faster and by how much, the faster/slower counts, and the biggest losses and gains. It follows the nested-segments choice, so it says what the panel says.

Under the counts, a bar per segment in course order shows the running total: above the dashed line activity 2 is behind, below it is ahead. Hovering a bar names the segment and the total there. It answers what the net cannot — whether the gap opened in one place or everywhere.

By default a segment inside another (a climb within a lap, a lap within a full-route segment) counts in both, since overlapping segments are often the interesting ones. Where Strava's page says where each effort sits in the ride, nested segments are marked inside … under their name and the summary offers to leave them out, which recounts the net and redraws the chart without counting any stretch of road twice. The table always keeps every row. The activity log says on each comparison whether positions were available at all.

Your history on a segment

“Compare vs my PRs” also fills a Your history column: where activity 1's effort ranks among all your efforts on that segment (“3rd of 12”), and a sparkline of your times from oldest to newest with your best marked. Faster is drawn higher, and each segment is scaled to its own range, so the shape is your progression there rather than a comparison between segments. Up to 60 of your most recent efforts are drawn; beyond that the label says “of last 60”.

Form

When both activities recorded heart rate, a Form column reads the two deltas together, which neither column says on its own:

Reading	What happened
Fitness	Faster at the same or a lower heart rate, or the same time at a lower one
Effort	Faster, but at a higher heart rate
Even	Same time, same heart rate
Easier	Slower at a lower heart rate
Slower	Slower at the same heart rate
Fading	Slower at a higher heart rate

A second of timing and two beats per minute are treated as noise, so riding a segment the same way twice reads Even.

Sorting

Click any column header to sort by it; click the same header again to reverse. Segments with no value in that column always sink to the bottom, in both directions, so an unreadable row never ranks as the fastest. The default order is activity 1’s page order, which is the order you rode them.

Compare vs my PRs

“Compare vs my PRs” adds two columns: your personal record on each segment, and how far activity 1 was off it. The PR is your all-time best, so if activity 1 is your own PR ride it shows 0:00; a negative value means activity 1 beat your PR.

Some caveats worth knowing:

• The PR is yours, as the signed-in Strava athlete. It is only meaningful when one of the two activities is yours
• It is read from your effort history on each segment (/athlete/segments/{id}/history, the JSON Strava’s own site uses), and the PR is your fastest elapsed time there. If that endpoint fails, the segment’s page is read instead, and the activity log says so and why
• Strava has no bulk PR endpoint, so this is one request per segment. It is capped at 60 segments per click, runs three at a time, and caches results for 24 hours, shared with “My Activities Here”. Clear does not empty that cache; “Refresh my PRs” reads every segment again, ignoring it, which is how a PR set since the last lookup shows up. A segment that fails to refresh keeps the copy it had
• Segments where the PR cannot be read show N/A. That means "unknown", not "no PR" — this reads what Strava serves rather than guessing
• A segment that could not be read — a rate limit, a network blip, or only its segment page answering — is cached for 10 minutes rather than 24 hours, so clicking again after that retries it

Export

Click “Export CSV” to download a CSV with headers that include the detected athlete names. It contains exactly the columns the table is showing, in the sort order you left it in.

Status coloring

• Time deltas and Time Diff %: positive = slower (red), negative = faster (green)
• Speed deltas: positive = faster (green), negative = slower (red)
• Pace deltas: positive = slower (red), negative = faster (green)
• Power and VAM deltas: positive = more (green), negative = less (red)
• Heart-rate deltas are not shaded: a lower heart rate is only good news if the time held up, so a colour would mislead as often as it helped

Shading intensity scales with the size of the delta: a full-strength tint is 60s of time, 10% of time, 5 km/h of speed, 30 s/km of pace, 50 W of power, or 200 m/h of VAM.

VAM

VAM is computed as distance × average grade ÷ time, for both activities alike. Strava fills in its own VAM only for categorized climbs, and it means little on flat ground, so segments averaging under 3% show N/A. On one segment the climb is the same for both activities, so the VAM delta is the time delta expressed in climbing units — useful for comparing across climbs, not new information within one.

How it works (high-level)

Getting the data for one activity takes the cheapest route that works, and falls back automatically when a route fails:

1. The activity is already open in a tab — the content script reads it directly. No new tabs, no fetching.
2. Some other strava.com tab is open — that tab fetches the activity HTML from its own origin (so your session cookie is sent), and the popup parses it with DOMParser.
3. Nothing relevant is open — the popup opens a background tab, waits for the content script to answer, reads the data, and closes the tab again. If you close the popup before it finishes, the service worker closes the tab instead.

A strava.com tab is only used for route 2 if its content script answers. Tabs opened before the extension was installed or updated are skipped until you reload them.

Segment data comes from the inline script that seeds Strava’s efforts list (pageView.segmentEfforts().reset(…)) rather than from the table: it has raw numbers (times, heart rate, power, grade), reads the same in every language and unit system, and is in the page’s HTML even for runs, whose table is only drawn after the page loads. The table is read only when that data is missing.

Files:

• extractor.js: all DOM reading. Every function takes an explicit Document, so the same code runs against a live page or against fetched HTML
• content-script.js: request/response bridge on strava.com — extract this page, fetch another activity, or look up your effort history on a segment (your PR and recent activities there; the segment page is the fallback for the PR). It only fetches from an allowlist of paths, and waits for the segments table with a MutationObserver instead of a fixed sleep
• popup.js: tab detection, route selection, comparison, rendering, CSV export. The table's columns are declared once in COLUMNS, which drives the headers, the cells and the CSV together
• utils.js: pure parsing and comparison helpers (times, speeds, paces, power, heart rate, VAM, distances, segment matching, sorting, summary, ranking your activities)
• background.js: MV3 service worker. Its one job is closing the background tabs a popup opened, if the popup is closed before it could

Development

Tests

npm install
npm test

utils.js and extractor.js are covered by unit tests; tests/popup.test.js loads the real popup.html and popup.js into jsdom with a stubbed chrome API and exercises the full comparison and rendering path. tests/background.test.js plays the popup's side of the service worker's port, including closing mid-run.

GitHub Actions runs npm test and npm run build on every push to main and every pull request, and keeps the packaged zip as a build artifact.

Styles

tailwind.output.css is hand-maintained plain CSS — a small subset of Tailwind-style utilities plus the extension's own component classes. Edit it directly. There is no CSS build step and no Tailwind dependency: the name is historical, and a tailwind.css source, a Tailwind config and a PostCSS config all used to sit here without ever being run.

Project structure (selected):

• manifest.json: Chrome MV3 manifest (name, version, permissions)
• popup.html, popup.js, tailwind.output.css: Popup UI and logic
• extractor.js, content-script.js: Reading data out of Strava pages
• utils.js: Parsing and comparison helpers
• tests/: Vitest suites
• icons/: Extension icons

Privacy

• No network requests to external servers are made by the extension
• Reads only Strava activity pages and the URLs of your open Strava tabs (for auto-detection). The extension holds no tabs permission, so tabs on other sites are invisible to it — host_permissions limits it to www.strava.com
• Comparison results are stored with chrome.storage.local to auto-restore the last view

Troubleshooting

• “No segments found”: Make sure you’re on an activity page that has segments and let the page fully load. Click Compare again
• Auto-detect didn’t find tabs: Ensure your tabs are https://www.strava.com/activities/<id> pages. Only Strava tabs are visible to the extension
• “Redirected away from the activity page”: You’re signed out, or the activity is private. Open it in a tab and compare again
• Athlete names missing or “unknown”: Not all pages expose the same metadata; this is expected sometimes
• “No personal records found”: You are either not signed in, or signed in as an athlete who has not ridden these segments. The PR columns stay hidden rather than filling with N/A
• “No Strava segment ids in this comparison”: The comparison was saved by 2.6, which could not read segment ids. Click “Compare Activities” again, then retry
• “Effort history unavailable … read their segment pages instead” in the log: Strava refused or changed the history endpoint, so PRs came from the slower, less reliable segment page. The message includes the first error
• Power or heart-rate columns missing: Neither activity recorded it, or Strava served data this version does not recognise. Runs usually have no power
• VAM columns missing: None of the matched segments averages 3% or steeper
• “My Activities Here” lists nothing: None of your 20 most recent activities on each segment is another activity than activity 1, or your effort history could not be read — the log says which
• Buttons are dimmed and do nothing: a comparison, PR lookup or “My Activities Here” search is still running. Only one runs at a time, and the buttons come back when it finishes
• “Could not copy the summary”: the browser refused clipboard access, usually because the popup lost focus. Click into the popup and try again
• Your PR or history looks out of date: it is cached for a day. Click “Refresh my PRs”
• If the popup shows stale data, click “Clear” to reset and re-run the comparison
• The activity log in the popup names the route used for each activity, which is the fastest way to see where a comparison went wrong

License

MIT — see LICENSE.md.