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Wayback CDX Server API - BETA

Table of Contents

Intro and Usage

Advanced Usage

Intro and Usage

The wayback-cdx-server is a standalone HTTP servlet that serves the index that the wayback machine uses to lookup captures.

The index format is known as 'cdx' and contains various fields representing the capture, usually sorted by url and date. https://archive.org/web/researcher/cdx_file_format.php

The server responds to GET queries and returns either the plain text CDX data, or optionally a JSON array of the CDX.

The CDX server is deployed as part of the Wayback Machine at https://web.archive.org and the examples below reference this deployment.

However, the CDX server software is freely available with the rest of the open-source Wayback software in this repository.

Further documentation will focus on configuration and deployment in other environments.

Please contant us at wwm@archive.org for additional questions.

Basic Usage

The simplest query uses only the single required parameter for the CDX server, url:

This will return index entries, one per row, describing each 'capture' of the url "archive.org" that is available in the archive.

The columns of each line are the fields of the cdx. At this time, the following cdx fields are publicly available:


It is possible to customize the Field Order as well.

The url= value should be url encoded if the url itself contains a query.

All the other params are optional and are explained below.

For doing large/bulk queries, the use of the Pagination API is recommended.

Url Match Scope

The default behavior is to return exact url matches. However, the cdx server can also return results matching a certain prefix, a certain host or all subdomains by using the matchType= param.

For example, if given the url: archive.org/about/ and:

  • matchType=exact (the default), it will return results matching exactly archive.org/about/

  • matchType=prefix will make it return all the results whose paths start with archive.org/about/

For example: http://web.archive.org/cdx/search/cdx?url=archive.org/about/&matchType=prefix&limit=1000

The matchType may also be set implicitly by using a wildcard '*' at the beginning or end of the url:

  • If the url ends with '/*', eg url=archive.org/* the query is equivalent to url=archive.org/&matchType=prefix
  • If the url starts with '*.', eg url=*.archive.org/ the query is equivalent to url=archive.org/&matchType=domain

(Note: The domain mode is only available if the CDX is in SURT-order format.)

Output Format (JSON)

 ["org,archive)/", "19970126045828", "http://www.archive.org:80/", "text/html", "200", "Q4YULN754FHV2U6Q5JUT6Q2P57WEWNNY", "1415"],
 ["org,archive)/", "19971011050034", "http://www.archive.org:80/", "text/html", "200", "XAHDNHZ5P3GSSSNJ3DMEOJF7BMCCPZR3", "1402"],
 ["org,archive)/", "19971211122953", "http://www.archive.org:80/", "text/html", "200", "XAHDNHZ5P3GSSSNJ3DMEOJF7BMCCPZR3", "1405"]]
  • By default, the CDX server returns gzip encoded data for all queries. To turn this off, add the gzip=false param.

Field Order

It is possible to customize which fields are returned from the cdx server (and their order) by using the fl= param. Simply pass in a comma seperated list of fields and only those fields will be returned:

For example: http://web.archive.org/cdx/search/cdx?url=archive.org&fl=timestamp,mimetype&output=json returns only the timestamp and mimetype fields with the header ["timestamp","mimetype"].

  • If the fl= param is omitted, all the available fields are returned.


  • Date Range: Results may be filtered by timestamp using from= and to= params. The ranges are inclusive and are specified in the same 1 to 14 digit format used for wayback captures: yyyyMMddhhmmss

    For example: http://web.archive.org/cdx/search/cdx?url=archive.org&from=2010&to=2011

  • Regex filtering: It is possible to filter on a specific field or the entire CDX line (which is space delimited). Filtering by a specific field is often simpler. Any number of filter params of the following form may be specified: filter=[!]field:regex

    • field is one of the named cdx fields (listed in the JSON query) or an index of the field. It is often useful to filter by mimetype or statuscode

    • Optional: a ! before the query inverts the match, that is, will return results that do NOT match the regex.

    • regex is any standard Java regex pattern (http://docs.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html)

For example: http://web.archive.org/cdx/search/cdx?url=archive.org&output=json&limit=2&filter=!statuscode:200 will return 2 capture results with non-200 status codes.

For example: http://web.archive.org/cdx/search/cdx?url=archive.org&output=json&limit=10&filter=!statuscode:200&filter=!mimetype:text/html&filter=digest:2WAXX5NUWNNCS2BDKCO5OVDQBJVNKIVV will return 10 capture results with non-200 status codes and mime types that are not text/html but which match a specific content digest


A new form of filtering is the option to 'collapse' results based on a field, or a substring of a field. Collapsing is done on adjacent cdx lines, causing all matching captures after the first one to be filtered out. This is useful for simplifying queries whose results are 'too dense' or when looking for unique captures.

To use collapsing, add one or more params of the form collapse=field or collapse=field:N where N is the first N characters of field to test.

For example: http://web.archive.org/cdx/search/cdx?url=google.com&collapse=timestamp:10 will only show at most 1 capture per hour (comparing the first 10 digits of the timestamp field). Given two captures whose timestamps are 20130226010000 and 20130226010800, since the first 10 digits (2013022601) match, the second capture will be filtered out.

The calendar page at web.archive.org uses this filter by default: http://web.archive.org/web/*/archive.org

For example: http://web.archive.org/cdx/search/cdx?url=archive.org&collapse=digest will only show unique captures (captures with different content digests). Note that only adjacent cdx lines are collapsed, duplicate digests elsewhere in the result set are not affected.

For example: http://web.archive.org/cdx/search/cdx?url=archive.org&collapse=urlkey&matchType=prefix will only show unique urls from a prefix query (filtering out captures except for the first capture of a given url). This is similar to the old prefix query in the Wayback Machine. (Note that this query may be slow at the moment.)

Query Result Limits

As the CDX server may return millions or billions of records, it is often necessary to set limits on a single query for practical reasons. The CDX server provides several mechanisms for this, including ability to return the last N as well as the first N results.

  • The CDX server config provides a setting for absolute maximum length returned from a single query (currently set to 150000 by default).

  • Queries can include the limit= N param to return the first N results. or the limit= -N param to return the last N results. The last-N query may be slow as it still reads all the results, and only avoids the cost of returning all but the last N to the client.

    For example: http://web.archive.org/cdx/search/cdx?url=archive.org&limit=-1 will return the last result.

  • Advanced Option: fastLatest=true may be set to return some number of latest results for an exact match and is faster than the standard last results search. The number of results is at least 1 so limit=-1 implies this setting. The number of results may be greater >1 when a secondary index format (such as ZipNum) is used, but is not guaranteed to return any more than 1 result. Combining this setting with limit= will ensure that no more than N last results.

For example: http://web.archive.org/cdx/search/cdx?url=archive.org&fastLatest=true&limit=-5 will return up to 5 of the latest (by date) results, more quickly than with just limit=-5.

  • The offset= M param can be used in conjunction with the limit= param to 'skip' the first M records. This allows for a simple way to scroll through the results.

    However, the offset/limit model does not scale well to large querties since the CDX server must read and skip through the number of results specified by offset, reqiring it to begin reading at the beginning every time.

Advanced Usage

The following features are for more specific/advanced usage of the CDX server.

Resumption Key

There is a new method that allows for the CDX server to specify a 'resumption key' that can be used to continue a query from where it previously ended. This allows a large query to be broken up into smaller queries more efficiently.

  • To show the resumption key add the showResumeKey=true param. When set, the resumption key will be included only if the query has more results that were excluded due to a limit= param (or the server-side max query limit).

  • At the end of the results, after a blank row, the will be output on a seperate line or in a seperate JSON array.

  • Plain text example: http://web.archive.org/cdx/search/cdx?url=archive.org&limit=5&showResumeKey=true

org,archive)/ 19970126045828 http://www.archive.org:80/ text/html 200 Q4YULN754FHV2U6Q5JUT6Q2P57WEWNNY 1415
org,archive)/ 19971011050034 http://www.archive.org:80/ text/html 200 XAHDNHZ5P3GSSSNJ3DMEOJF7BMCCPZR3 1402
org,archive)/ 19971211122953 http://www.archive.org:80/ text/html 200 XAHDNHZ5P3GSSSNJ3DMEOJF7BMCCPZR3 1405
org,archive)/ 19971211122953 http://www.archive.org:80/ text/html 200 XAHDNHZ5P3GSSSNJ3DMEOJF7BMCCPZR3 1405
org,archive)/ 19980109140106 http://archive.org:80/ text/html 200 XAHDNHZ5P3GSSSNJ3DMEOJF7BMCCPZR3 1402
 ["org,archive)/", "19970126045828", "http://www.archive.org:80/", "text/html", "200", "Q4YULN754FHV2U6Q5JUT6Q2P57WEWNNY", "1415"],
 ["org,archive)/", "19971011050034", "http://www.archive.org:80/", "text/html", "200", "XAHDNHZ5P3GSSSNJ3DMEOJF7BMCCPZR3", "1402"],
 ["org,archive)/", "19971211122953", "http://www.archive.org:80/", "text/html", "200", "XAHDNHZ5P3GSSSNJ3DMEOJF7BMCCPZR3", "1405"],
 ["org,archive)/", "19971211122953", "http://www.archive.org:80/", "text/html", "200", "XAHDNHZ5P3GSSSNJ3DMEOJF7BMCCPZR3", "1405"],
 ["org,archive)/", "19980109140106", "http://archive.org:80/", "text/html", "200", "XAHDNHZ5P3GSSSNJ3DMEOJF7BMCCPZR3", "1402"],


There is some work on custom counters to enchance the aggregation capabilities of the CDX server. These features are brand new and should be considered experimental.

Duplicate Counter

While collapsing allows for filtering out adjacent results that are duplicates, it is also possible to track duplicates throughout the cdx using a special new extension. By adding the showDupeCount=true param a new dupecount column will be added to the results.

Skip Counter

It is possible to track how many CDX lines were skipped due to Filtering and Collapsing by turning on the special skipcount column with showSkipCount=true. An optional endtimestamp column can also be shown, containing the timestamp of the most recent capture, by adding lastSkipTimestamp=true

Pagination API

The resumption key described above allows for the sequential querying of CDX data. However, in some cases where very large result sets are needed (for example with a matchType=domain query), it may be useful to perform queries in parallel and also to estimate the total size of the query without running it in full.

The wayback and cdx-server software support secondary loading from a 'zipnum' CDX index. Such an index contains CDX lines stored in concatenated GZIP blocks (usually 3000 lines each) and a secondary index which provides a binary search to the 'zipnum' blocks. By using the secondary index, it is possible to estimate the total size of a query and also to break up the query. Using the zipnum format or another secondary index is needed to support pagination.

However, pagination can only work on a single index at a time. Merging input from multiple sources (plain cdx or zipnum) is not possible with pagination. As such, the results from the paginated version may be slightly less up-to-date than the default non-paginated query.

Access Control

The cdx server is designed to improve access to archived data by a broad audience, but it may be necessary to restrict certain parts of the cdx data.

The cdx server provides a way to grant permissions to access restricted data via an API key that is passed in as a cookie.

Currently two restrictions/permission types are supported:

  • Access to certain urls which are considered private. When restricted, only public urls are included in query results and access to the secondary index is restricted.

  • Access to certain fields, such as the filename in the CDX. When restricted, the cdx results contain only public fields.

To allow access, the API key cookie must be explicitly set on the client, eg:

curl -H "Cookie: cdx-auth-token=API-Key-Secret http://mycdxserver/search/cdx?url=..."

The API-Key-Secret can be set in the cdx server configuration.

CDX Server Configuration


Start by editing the wayback-cdx-server-servlet.xml file in the WEB-INF Directory. Just put some valid CDX-Files in the cdxUris-List (Files must end with cdx or cdx.gz!)