Create a release branch in SVN

See "Tag related svn files".

Once the branch is created, only changes necessary for the target release are merged in from the trunk.

Upgrade LocaleExplorer and other demos/samples

... to the ICU project site.

Build the icuapps module following the README's. Update code and/or docs as needed. "Reference" platforms for icuapps are: RedHat Linux and win32. On Linux, icuapps is built against the "make install "'ed ICU. So, run ICU4C's configure with --prefix=/some/where pointing to where ICU4C should be installed, and also follow icuapps's README.

Install the new locale explorer and other demos/samples onto the public demo hosting site.

ICU Collation Demo

Update the ICU collation demo's index.html with the new ICU version’s available collators.

  1. Do a clean build (configure, make clean, make install, make check).
    1. Otherwise, the data build may not pick up a new locale into the coll/res_index.txt file.
  2. Run icu-demos > webdemo/collation/ (after modifying it for your system).
  3. Copy-paste the output available-collators.txt into index.html.
    1. Or, easier: Use a GUI difftool (e.g., meld) to compare the two and move the changes into index.html.
    2. meld webdemo/collation/index.html ../available-collators.txt
  4. See for example the changes for ICU-11355

For details see the comments at the start of the file.

Repository Branch and Tags

Careful! The following examples contain specific version, revision and ticket numbers. Adjust them for the current release! Easiest: Paste into an editor, fix, then paste into the terminal.

Creating Maintenance Branch.

Sanity check: Update to the lastest repository revision. (Master branch if you copy from master, maintenance branch if you copy from there.)

git checkout master
git pull upstream master
git log -n1
commit bcd0... (HEAD -> master, upstream/master, ...)

Ensure that your local branch is in sync with the upstream branch.  Make sure you are checking the upstream remote, and not your fork!

Build & test ICU4C & ICU4J on your machine.

Create the maintenance branch from the current known good master ref.

git checkout -b maint/maint-63
git push -u upstream maint/maint-63


Use the GitHub GUI to create both the "release" and the "tag" at the same time:

Fill in the tag name, such as "release-63-rc" or "release-63-1", and make the target the "maint/maint-xx" branch (such as maint/maint-63).

Set the title to "ICU 63 RC" or "ICU 63.1".  Fill in the description using the text from the announcement email. (You can also look at previous releases and possibly re-use some of the generic text, such as links to the API docs, etc.)

For the release candidate tag, check the box that says "Pre-Release".

Your screen should look like this:

Until GitHub better supports Git LFS files, we should also continue to add the following text as well:

*Note: Please ignore the “Source code” zip & tar.gz files.* (They are auto-generated by GitHub and omit the LFS file contents.) 

Click the "Publish Release" button to make the tag.

If tagging a stable version (not release candidate), update the "latest" tag.
The "latest" tag is no longer updated. It was agreed by the ICU-TC to be deleted around the 64.2 time-frame, as it doesn't work well with with Git. (You need to force-push the new tag, and if somebody has already cloned the repository, they might have something different for the "latest" tag).
A possible future alternative might be a sym-link folder, or HTTP redirect that points to the latest release.

Maintenance release

Create the maintenance release tag from the maintenance branch, as above.

Update the "latest" tag.

ICU 58 and earlier

Tag related svn files, for icu, icu4j and (for final releases) tools file trees. We tag the tools tree so that we can reproduce the Unicode tools that were used for the Unicode data files in this release.

For a Release Candidate, just tag, don't branch, and only tag icu & icu4j.

For the final release, branch then tag. Copy the trunk to maint/maint-4-8 and copy that to tags/release-4-8. Specify the source revision explicitly via -r so that you don't inadvertently pick up an unexpected changeset. Make sure that the trunk at the source revision is good.

We do not tag the data & icuapps trees. Steven Loomis writes on 2011-may-23:

My thought had been (in the CVS days) to take a 'snapshot' of these items. However, in SVN all you need is a date or a revision number (such as r30140).

So, probably, we don't need to tag these two (icuapps or data).

Tools are more important because those tools are actually used in the release.

Create ICU download page

Create the download page before the first milestone, if we have one, or before the release candidate.

Log into the ICU homepage Google Site. (If you don't have write access, ask one of the editors to grant you access.)

Verify that there is not already a page for the upcoming release: Either via the sitemap, or on the bottom of the main download page where it says something like "Subpages (27): View All".

Copy the download page for the last release: Go to that page, gear menu, Copy page; "Name your page" using just the major version number for now (e.g., "61") so that the page URL is just that number, select "Put page under Downloading ICU", click the red COPY button.

Adjust the new page as needed: Change the title to "Download ICU 61 Release Candidate" (with the right version number...), remove contents specific to the previous release, update all version numbers, update all links.

Put a big, bold+italics, red warning at the top like "This version has not been released yet. Use it for testing but not in production!"

Save the page. It is generally a good idea to save frequently. For further edits, simply go back into edit mode. (Keyboard shortcut 'e' for edit, ctrl+s for save.)

Add new contents for the upcoming release: Grab some text from the sibling Unicode and CLDR release notes, look at the proposal status doc for this release, make a pass through the api/enhancement tickets fixed in this release or under reviewing/reviewfeedback.

Look at the download pages of the last two releases for templates for things like a Migration Issues section etc.

Ask everyone on the team to add stuff & details.

Once the page has been created and various people are invited to edit it, everyone should keep editing short so that the page is not locked for others for long periods of time.

Maintenance release

For a maintenance release, look at the ICU 60 page which includes 60.2.

Milestone on the main download page

We had the following HTML on the main download page for ICU 4.8M1 = 4.7.1:

<h3 style="background-color:rgb(102, 102, 102);color:white;margin-bottom:0pt;margin-top:12pt;padding-left:0.75em;font-size:1em;font-family:Arial,Helvetica,sans-serif">Development Milestones</h3>
<table border="0"><p style="font-size:10pt;font-family:Arial,Helvetica,sans-serif">Development milestone versions of ICU can be downloaded below. A development milestone is a stable snapshot build for next ICU major version.  These binaries and source code are provided for evaluation purpose and should be not be used in production environments.  New APIs or features in a milestone release might be changed or removed without notice.&nbsp;</p>
<td style="width:105px;height:16px">&nbsp;<b>Release</b></td>
<td style="width:792px;height:16px">&nbsp;<b>Major Changes<br>
<td style="width:105px;height:29px">&nbsp;<a href="">4.8M1 (4.7.1)</a><br>
<td style="width:792px;height:29px">&nbsp;CLDR 1.9.1+, Parent locale override, Dictionary type trie, Alphabetic index (C), Compound text encoding (C), JDK7 Locale conversion (J)<br>

Upload Release Source/Binaries

Download Directories are located at, for example,
corresponding to

Look at previous releases for an example.

Java Source/Bin:   See Building ICU4J Release Files

C source/binary: WORK IN PROGRESS

  • Source and Linux Bins: requirements:   Unix make + docker
  • (You need to install docker and docker-compose, do not proceed until docker run hello-world works!)
    • $ git clone
    • $ cd icu-docker/src
    • $ git clone --branch release-64-rc --depth 1
    • $ cd icu
    • $ git lfs fetch
    • $ git lfs checkout
    • $ cd ../..
    • $ less
    • Follow those instructions.
    • Source and binaries will show up in ./dist/ but the names don't match what's needed on output.
  • Note: If you only want to make a source tarball (.tgz/.zip), then you can run `make dist`.
    • This will produce a source tarball and will include a pre-compiled .dat file under icu4c/source/data/in/. (This tarball will also omit all of the data sub-directories containing locale data).
    • Note that the source is taken from the git repository itself, and not your local checkout. (Thus it will exclude any local uncommitted changes).
  • Windows Bin:
    • Manual process:
      • Build with MSVC x64 Release. (See the ICU readme.html file for details).
      • Open a command prompt.
      • > cd C:\icu\icu4c\  (or wherever you have ICU located).
      • > powershell
      • > Set-ExecutionPolicy -Scope Process Unrestricted
      • > .\packaging\distrelease.ps1 -arch x64
      • This will produce the file "source\dist\", which will need to be renamed before uploading.
        • For example, the binaries for ICU4C v61.1 generated with VS2017 were named "".
    • Using the output from the build bots:
      • Navigate to the GitHub page for the commits on the "maint/maint-<version>" branch.
        • Ex:
      • Click on the green check mark (✔) on the most recent/last commit. (It might be a red X if the builds failed, hopefully not).
        • This will open up a pop-up with links to various CI builds.
      • Click on one of the various links that says "Details" for the Azure CI builds.
        • This will open up the GitHub overview of the build status.
        • Azure CI Builds &quot;Details&quot; link

      • Click on the link "View more details on Azure Pipelines" link.
        • This will take you to the actual Azure CI build page.
      • On the top right of the page there should be a button titled "Artifacts". Click this and it should show a drop-down with various ZIP files that you can download.
        • Azure CI Builds Artifacts Button

      • The ZIP may automatically download for you.
      • However, if you are signed-in to then you might see a dialog titled "Artifacts explorer".
      • In this case click on the name, then the "..." button to download the zip file.
        • Azure CI Builds Download zip

      • Download both the x64 (64-bit) and x86 (32-bit) ZIP files.
      • For each architecture:
        • Extract the Zip file. (It will have a name like "").
        • Navigate into the folder with the same name.
        • Rename the file "" to the appropriate name:
          • Ex: The x64 zip for version 64.1 was named ""
          • Ex: The x86 zip for version 64.1 was named ""
        • Note: For RC releases the name looked like this: ""
  • AIX Bin: (AIX is broken and ignored for now.)
    • login to and copy the ICU4C source archive created above to there.
    • $ gzip -dc icu4c-XXX-src.tgz | tar xf -
    • $ cd icu
    • $ PATH=/opt/IBM/xlC/13.1.3/bin:$PATH source/runConfigureICU AIX
    • (The above command line doesn't actually work, see ICU Ticket #13639 for a workaround.)
    • $ gmake DESTDIR=/tmp/icu releaseDist
    • That last step will create a directory in /tmp/icu - zip that up to make the release.
    • In case /tmp happens to be full, see the mailing list archive for advice.
PGP files:
Sign all archives created above with your own personal PGP key:
gpg --armor --detach-sign
MD5 files:
Create three different '.md5' files for icu4j (all files),  icu4c (source) and icu4c (binaries).
Use cfv: like this to create a .md5 file:
cfv -t md5 -C -f icu-……-src.md5 somefile.tgz
To verify, just run "cfv -f icu-……-src.md5" and it will verify that the md5 file contains hashes for all referenced files.


Create a SHASUM512.txt file  with:

shasum -a 512 *.zip *.tgz | tee SHASUM512.txt

This file should also be GPG signed.

Update the Download Page Gadgets

Update the gadgets on the download page to point at the new URL for the binaries.
  1. Edit the download page.
  2. Click on the Gadget area.
  3. Click on the "gear" icon.
  4. Update the URL field with the new URL.
    1. For example: The ICU4C 63.1 Binaries URL was:

Check the ICU public site for the new release

Make sure that, aside from download pages, homepages, news items, feature lists and feature comparisons, etc. are updated. Upload the new API references. Update the User Guide.

Update the Trac release number list for ICU4C and ICU4J.

Update the ICU release number list by going to "Admin>Versions" in Trac, and add the new ICU version.

Post-release cleanup

  • Cleanup the milestone in the ICU Trac. Move left over items to future milestones. Close the milestone.
  • Look for TODO comments in the source code and file new tickets as required.
  • Delete and retag latest (ONLY after GA release, including maintenance!)
    • svn delete latest
    • svn cp <the latest tags/release-###  tag>  latest

Update online demos

Update online demos/tools to the latest version:

Online information update

Collation and comparison charts need to be updated. See charts/Performance & Size.

Old sensitive tickets

Unset the "sensitive" flag on old tickets. For example, on tickets that were fixed two or more releases ago.

Sample ticket query for ICU 65, for tickets fixed in 63 or earlier. Adjust the fixVersion selection as appropriate. Check the list in the ICU meeting.

Check duplicates and fixedbyotherticket! Keep the "sensitive" flag on tickets that were closed as duplicates of other tickets that are not yet fixed or have been fixed only very recently.

For removing the flag:

  • Enter bulk edit. Select all query results.
  • Uncheck duplicates of unfixed or too-recent tickets.
  • Edit fields:
    • Security Level = None
    • Add label "was_sensitive"
    • No notification emails
  • Confirm bulk edit.

Punt tickets

Double-check that tickets with commits in this release are closed/fixed. Close as needed. (Hopefully none misticketed at this point...)

Then punt remaining tickets marked for this release:

  1. In Jira, search for all tickets with Project=ICU, Fix Version=<this release>, Status≠Done.
  2. Go to Bulk Edit ("..." menu in the upper right corner)
  3. Select all
  4. Edit fields:
    1. Fix Version: replace all with "future"
    2. Labels: add "punt<this release>" (e.g., "punt63")
    3. No email notifications
  5. Confirm bulk edit
  6. Send a courtesy email to the team with a Jira query URL for the Label="punt<this release>" tickets.
After punting, please also update the "To-Do for Next ICU Release" widget on Jira.
  1. Open
  2. Use the drop-down to change the fix version to the next ICU version
  3. Click "Save" next to the filter title

Update readme

Update ICU4C readme.html and ICU4J readme.html before every milestone (GA / RC / Milestone-N). Make sure following items are up to date.

  • Release version
  • Last update date
  • Description - descriptions for GA, RC and Milesone-N are already included in the readme file. If the readme should remain the same between milestones, we can skip directly to the GA description. Otherwise, pick the right one for the release type.
  • Build steps - make sure supported compiler versions are up to date