diff --git a/ia-cdx-search b/ia-cdx-search
index c0c194a..3d023e8 100755
--- a/ia-cdx-search
+++ b/ia-cdx-search
@@ -1,4 +1,6 @@
 #!/usr/bin/env python3
+import asyncio
+import collections
 import json
 import re
 import shlex
@@ -6,8 +8,72 @@ import sys
 import urllib.request
 
 
-if len(sys.argv) not in (2, 4) or sys.argv[1].lower() in ('-h', '--help') or re.search(r'(^|&)(output|limit|resumekey|showresumekey|page|shownumpages)=', sys.argv[1], re.IGNORECASE):
-	print('Usage: ia-cdx-search QUERY [PAGE NUMPAGES]', file = sys.stderr)
+def fetch(url):
+	print(f'GET {url}', file = sys.stderr)
+	req = urllib.request.Request(url)
+	with urllib.request.urlopen(req) as r:
+		if r.code != 200:
+			raise RuntimeError(f'Could not fetch {url}')
+		code = r.code
+		o = json.load(r)
+	return url, code, o
+
+
+async def wait_first_and_print(tasks):
+	if not tasks:
+		return
+	task = tasks.popleft()
+	url, code, o = await task
+	print(f'{code} {url}')
+	assert o, 'got empty response'
+	fields = o[0]
+	assert all(len(v) == len(fields) for v in o[1:]), 'got unexpected response format'
+	for row in o[1:]:
+		print(json.dumps(dict(zip(fields, row))))
+	return task._ia_cdx_page
+
+
+async def main(query, concurrency = 1, startPage = None, numPages = None):
+	assert (startPage is None) == (numPages is None)
+	baseUrl = f'https://web.archive.org/cdx/search/cdx?{query}'
+	if startPage is None:
+		url = f'{baseUrl}&showNumPages=true'
+		numPages = int(fetch(url)[2])
+		startPage = 0
+		print(f'{numPages} pages', file = sys.stderr)
+
+	loop = asyncio.get_running_loop()
+	tasks = collections.deque()
+	lastGoodPage = -1
+	try:
+		try:
+			for page in range(startPage, numPages):
+				while len(tasks) >= concurrency:
+					lastGoodPage = await wait_first_and_print(tasks)
+				url = f'{baseUrl}&output=json&page={page}'
+				task = loop.run_in_executor(None, fetch, url)
+				task._ia_cdx_page = page
+				tasks.append(task)
+			while len(tasks) > 0:
+				lastGoodPage = await wait_first_and_print(tasks)
+		except:
+			# It isn't possible to actually cancel a task running in a thread, so need to await them and discard any additional errors that occur.
+			try:
+				await asyncio.gather(*tasks)
+			except:
+				pass
+			raise
+	except (RuntimeError, json.JSONDecodeError, AssertionError):
+		concurrencyS = f'{concurrency} ' if concurrency != 1 else ''
+		print(f'To resume this search from where it crashed, run: ia-cdx-search {shlex.quote(query)} {concurrencyS}{lastGoodPage + 1} {numPages}', file = sys.stderr)
+		raise
+	except (BrokenPipeError, KeyboardInterrupt):
+		pass
+
+
+args = sys.argv[1:]
+if len(args) not in (2, 3, 4) or args[0].lower() in ('-h', '--help') or re.search(r'(^|&)(output|limit|resumekey|showresumekey|page|shownumpages)=', args[0], re.IGNORECASE):
+	print('Usage: ia-cdx-search QUERY [CONCURRENCY] [PAGE NUMPAGES]', file = sys.stderr)
 	print('Please refer to https://github.com/internetarchive/wayback/tree/master/wayback-cdx-server for the relevant query parameters', file = sys.stderr)
 	print('The output, limit, resumeKey, showResumeKey, page, and showNumPages parameters must not be included.', file = sys.stderr)
 	print('To resume a search that failed for some reason, provide the page number and number of pages through the second argument instead.', file = sys.stderr)
@@ -19,36 +85,10 @@ if len(sys.argv) not in (2, 4) or sys.argv[1].lower() in ('-h', '--help') or re.
 	print(" - Subdirectories: ia-cdex-search 'url=example.org&collapse=urlkey&fl=original&matchType=domain&filter=original:^https?://[^/]*example\.org(?::[0-9]*)?/[^/]*/'", file = sys.stderr)
 	print('   The same caveat applies. The directory must have been retrieved directly without an additional trailing path or query string.', file = sys.stderr)
 	sys.exit(1)
-
-query = sys.argv[1]
-baseUrl = f'https://web.archive.org/cdx/search/cdx?{query}'
-if sys.argv[2:]:
-	startPage, numPages = map(int, sys.argv[2:])
-else:
-	url = f'{baseUrl}&showNumPages=true'
-	print(f'GET {url}', file = sys.stderr)
-	req = urllib.request.Request(url)
-	with urllib.request.urlopen(req) as r:
-		if r.getcode() != 200:
-			raise RuntimeError(f'Could not fetch number of pages')
-		numPages = int(r.read())
-	startPage = 0
-	print(f'{numPages} pages', file = sys.stderr)
-
-try:
-	for page in range(startPage, numPages):
-		url = f'{baseUrl}&output=json&page={page}'
-		print(f'GET {url}', file = sys.stderr)
-		req = urllib.request.Request(url)
-		with urllib.request.urlopen(req) as r:
-			if r.getcode() != 200:
-				raise RuntimeError(f'Could not fetch {url}')
-			o = json.load(r)
-		assert o, 'got empty response'
-		fields = o[0]
-		assert all(len(v) == len(fields) for v in o[1:]), 'got unexpected response format'
-		for row in o[1:]:
-			print(json.dumps(dict(zip(fields, row))))
-except (RuntimeError, json.JSONDecodeError, AssertionError):
-	print(f'To resume this search from where it crashed, run: ia-cdx-search {shlex.quote(query)} {shlex.quote(page)} {shlex.quote(numPages)}', file = sys.stderr)
-	raise
+query = args[0]
+kwargs = {}
+if len(args) in (2, 4):
+	kwargs['concurrency'] = int(args[1])
+if len(args) in (3, 4):
+	kwargs['startPage'], kwargs['numPages'] = map(int, args[-2:])
+asyncio.run(main(query, **kwargs))